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Introduction Triple negative breast cancer (TNBC) is a heterogeneous breast cancer subtype which continues to portend a particularly poor prognosis compared to other breast cancer subtypes. Immune checkpoint inhibitor (ICI) therapies have emerged as promising options for locally advanced and metastatic TNBC. However, clinical trials have demonstrated mixed results with respect to ICI response. Given varied outcomes and the potential for immune-related adverse events associated with ICIs, there is critical need for identification of accurate biomarkers of response and improved strategies to counteract ICI resistance and/or toxicity. Methods Advanced immunoprofiling of peripheral blood mononuclear cells (PBMCs) and plasma from 7 metastatic TNBC patients with variable responses to anti-PD1 or anti-PDL1 therapy was performed. Samples were analyzed from blood draws obtained: (i) prior to first administration, (ii) while receiving ICI treatment, and (iii) at the time of conformed clinical progression or response to therapy. Response was determined by standard radiological assessment. Immunoprofiling included high parameter flow cytometry, single cell transcriptomics (10x genomics) and secretome analysis (Isoplexis). Single cell RNA profiles from 63,984 cells were analyzed. Results High parameter flow cytometry identified higher circulating levels of a subpopulation of activated CD4+ T cells with a phenotype of CXCR3low CD62Llow CD45RAhigh and CD57high expression in responders versus non-responders. Higher effector function of CD4+ T cells was corroborated by significantly elevated plasma concentrations of IL-2 (p=0.02) and IL-5 (p< 0.0001) among responders. Single cell transcriptomic analysis revealed clusters of B and T cells with distinct activation patterns that were associated with radiographic response. Strikingly, genes involved in B cell activation and T cell-B cell conjugation such as CD81 were found to be highly upregulated among CD4+ T cells from responders. Conclusions Our results are consistent with previous reports describing an association of increased B cell activity in TNBC with improved overall survival. We identified a subpopulation of CD4+ T cells with effector functions consistent with type 2 helper T cells that may not only target cancer cells by direct cytotoxic function, but also promote increased B cell anti-tumor activity. Our study provides insight into specific mechanisms of immune cell interplay that may drive response to ICI therapy. These cell populations and their associated pathways may represent potential biomarkers of response and/or targets for resistance reversal. Citation Format: Avia D. Wilkerson, Patricia A. Rayman, Paul G. Pavicic Jr, Hana Husic, Vladimir Makarov, Ivan Juric, Timothy Chan, Alberto J. Montero, Marcela Diaz-Montero. A multiomic approach to the identification of immune signatures of anti-PD1/PDL1 therapy responders in metastatic triple negative breast cancer: new implications in the role of helper T-cell and B-cell interplay [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-04-04.

BackgroundThe RxPONDER trial found that among breast cancer patients with estrogen receptor positive (ER+) breast cancer, 1-3 positive axillary nodes, and a recurrence score of ≤25, only pre-menopausal women benefitted from adjuvant chemoendocrine therapy; postmenopausal women with similar characteristic did not benefit from adjuvant chemotherapy. We aimed to replicate the RxPonder trial using a larger patient cohort with real world data to determine whether a RS threshold existed where adjuvant chemotherapy was beneficial regardless of age.MethodsThe National Cancer Database (NCDB) was queried for women with ER+, human epidermal growth factor receptor 2 (HER2) negative breast cancer, 1-3 positive axillary nodes, and RS ≤25 who received endocrine (ET) only or chemo-endocrine therapy (CET). Cox regression interaction was explored between CET and age as a surrogate for menopausal status.ResultsThe final analytic cohort included 28,427 eligible women: 7,487 (26.3%) received adjuvant CET and 20,940 (73.7%) ET. In the entire cohort, RS had a normal distribution, with a median score of 14. After correcting for demographic and clinical variables, a threshold effect was observed with RS >20 being associated with a significantly inferior overall survival (OS) (P value range: < 0.001-0.019). In women with RS of 20-25, CET was associated with a significant improvement in OS compared to ET alone, regardless of age (age 50: HR=0.521, P=0.019).ConclusionAmong women with ER+/HER2- breast cancer with 1–3 positive nodes, and a RS of 20-25—in contrast to the RxPONDER trial—we observed that CET was associated with an OS benefit in women regardless of age.

Background Metastatic hormone receptor positive (HR+)/human epidermal growth factor receptor-2 negative (Her2−) breast cancer remains a significant cause of cancer-related mortality. First-line treatment with endocrine therapy (ET) with a cyclin-dependent kinases 4 and 6 inhibitor (CDK4/6i) has largely become the standard systemic therapy. Following progression, no prospective randomized data exist to help guide second-line treatment. Materials and Methods This study used a nationwide electronic health record (EHR)-derived de-identified database, specifically analyzing 1210 patients with HR+/Her2− metastatic breast cancer (MBC) who were treated in the first-line setting with a CDK4/6i from the years 2015-2020. The aim of this study was to assess what therapies were given after first-line progression on CDK4/6i and to observe treatment patterns over time. Determination of second-line treatment efficacy, specifically assessing real-world progression-free survival (rwPFS) and overall survival (OS) was performed. Results A total of 839 patients received a documented second-line therapy after progression on first-line CDK4/6i treatment. Chemotherapy was chosen for 29.7% of patients, and the use of chemotherapy decreased over time. Three hundred two (36.0%) of patients continued a CDK4/6i. Data were adjusted for age, race, Eastern Cooperative Oncology Group (ECOG) performance status, stage at breast cancer diagnosis, and insurance payer type. Continuation of the CDK4/6i was associated with improved rwPFS (HR 0.48, 95% CI 0.43-0.53, P < .0001) and OS (HR 0.30, 95% CI 0.26-0.35, P < .0001) compared to chemotherapy. A majority of these patients continued the same CDK4/6i in the second-line setting, as was given in the first-line setting. Conclusion While prospective data are needed, analysis of real-world data suggests a survival benefit for continuation of a CDK4/6i beyond frontline progression for patients with HR+/Her2− MBC.

BackgroundCardiovascular disease (CVD) is the leading cause of death in men with prostate cancer (PC). Accumulated stress plays an important role in CVD development. The cumulative burden of chronic stress and life events can be measured using allostatic load (AL).MethodsThe initial cohort included males aged 18 years and older diagnosed with PC (2005-2019). AL was modeled as an ordinal variable (0-11). Fine-Gray competing risk regressions measured the impact of precancer diagnosis AL and postdiagnosis AL in 2-year major cardiac events (MACE). The effect of AL changes over time on MACE development was calculated via piecewise Cox regression (before, and 2 months, 6 months, and 1 year after PC diagnosis).ResultsWe included 5261 PC patients of which 6.6% had a 2-year MACE. For every 1-point increase in AL before and within 60 days after PC diagnosis, the risk of MACE increased 25% (adjusted hazard ratio [aHR] =1.25, 95% confidence interval [CI] = 1.18 to 1.33) and 27% (aHR = 1.27, 95% CI = 1.20 to 1.35), respectively. Using AL as a time-varying exposure, the risk of MACE increased 19% (aHR = 1.19, 95% CI = 1.11 to 1.27), 22% (aHR = 1.22, 95% CI = 1.14 to 1.33), 28% (aHR = 1.28, 95% CI = 1.23 to 1.33), and 31% (aHR = 1.31, 95% CI = 1.27 to 1.35) for every 1-point increase in AL before, 2 months after, 6 months after, and 1 year after PC diagnosis, respectively.ConclusionAL and its changes over time are associated with MACE in PC patients, suggesting a role of a biological measure of stress as a marker of CVD risk among men with PC.

Background: CDK 4/6 inhibitors (CDKI) with Endocrine therapy (ET) is mainstay treatment for hormone receptor-positive (HR+) Her2- metastatic breast cancer (MBC). Despite excellent efficacy, most patients develop resistance to CDKI limiting its utility. CDK4/6 are thought to act by upregulating VEGF causing tortuous angiogenesis and promoting cancer progression. Recent studies have shown aggressive tumors possess a higher density and tortuous vasculature. In this study, we evaluated if vascular radiomic features computationally extracted from liver CT scans pre- and post CDKI treatment could predict patient survival and treatment response. Method: From a registry of 350 patients on treatment with CDKI at institution 1(S1), 51 pts with HR+, Her2-, MBC patients with evidence of liver mets and disease progression (PFS) data were identified. 30 pts discontinued treatment due to progression or death, with a median time to progression of 195 days. Pre-treatment and first post-treatment CT exams were analyzed from 25 and 34 patients, respectively. Median time between scans was 128 days. To validate the prognostic value of our signature, a cohort of 29 patients with available OS data was identified from institution 2 (S2). A publicly available pre-trained deep learning model was applied to isolate liver metastases and vessels. Next, fast marching algorithm was applied to reduce vessels to their centerlines and divide the vasculature into constituent branches. 7 quantitative metrics were computed measuring vascularity of metastases and 3-D shape of hepatic vessels. First, the number (f1) and percentage (f2) of hepatic vessels arising from the tumor were computed. Vessel tortuosity - measuring the degree of twisting across a vessel - was computed separately for each branch. The mean (f3), standard deviation (f4), maximum (f5), skewness (f6), and kurtosis (f7) tortuosity values were calculated to summarize these measurements at patient level. The features were individually assessed at pre- and post-treatment for association with PFS at S1 in univariable Cox proportional hazards models. Features found to be associated in S1 were evaluated for association with OS in S2. Results: On the initial post-treatment scan, features of both tumor vascularization (f6 - HR=1.115 [1.039-1.196]; f7 - HR=10.646 [2.539-44.641]), as well as two features of vessel tortuosity (f3 - HR=0.011 [0.001-0.199]; f4 - HR=0.545 [0.313-0.949]) were significantly associated with PFS. Both tortuosity features were also significantly associated with OS in S2 (f3 - HR=0.085 [0.009-0.780]; f4 - HR=0.331 [0.130-0.842]). In addition the percentage (f7 - HR=6.445 [2.001-20.753]]),of vessels feeding the lesions was also significant in S2 while the number (f6 - HR=1.070 [0.966-1.184]), of vessels was not. No vessel metrics from the pre-treatment baseline exam were significantly associated with OS. Conclusions: Radiomic analysis of tumor vascularity and vessel tortuosity on CT scans post-CDK treatment was associated with patient survival and treatment response. Table 1.Association of vessel features with PFS in Institution 1(S1)and OS in Institution 2(S2)S1- Pretreatment CT (n=25)S1 - Post-Treatment CT (n=34)S2 - Post-treatment CT - Validation (n=29)f1Tortuosity - Mean0.9912702470.852294696–f2Tortuosity - St. Dev0.7563942230.273115373–f3Tortuosity - Max0.1387051870.0022517550.02931473f4Tortuosity - Skewness0.254463710.0318270370.02022882f5Tortuosity - Kurtosis0.3058266760.108967601–f6Number of vessels feeding lesions0.419096650.0025747910.19306052f7Percentage of vessels feeding lesions0.0517942660.0012205950.00179103 Citation Format: Vidya Sankar Viswanathan, Nathaniel Braman, Priyanka Reddy, Siddharth Kunte, Jame Abraham, Alberto J Montero, Anant Madabhushi. Post-treatment vascularity and vessel shape are associated with survival and response to CDK4/6 inhibitors in hormone receptor-positive metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-27.

Background: HER2-targeted therapies have led to marked improvements in survival for patients with HER2-positive breast cancer. Despite the gains obtained with current HER2-targeted therapies, an unmet medical need remains for patients with HER2-expressing (high or low expression) advanced breast cancer that has progressed after prior treatments. Zanidatamab is a novel HER2-targeted bispecific antibody that has multiple mechanisms of action, including immune clearance of HER2-expressing tumor cells through antibody-dependent cellular phagocytosis. Zanidatamab has been shown to be well-tolerated and has demonstrated antitumor activity, both as monotherapy and in combination with chemotherapy, across HER2-expressing solid tumors in a Phase 1 study. ALX148 is a high affinity CD47-blocking fusion protein with an inactive human immunoglobulin Fc region designed to enhance the activity of anticancer therapies, including antibodies, with minimal added hematologic toxicity. Treatment with zanidatamab in combination with ALX148 has the potential to augment the immune clearance of HER2-expressing cancer cells by blocking the CD47-SIRPa interaction that inhibits phagocytosis of the same cancer cells. In a Phase 1 study, ALX148 demonstrated antitumor activity when combined with trastuzumab in patients whose disease had progressed on prior HER2-targeted therapies. Here, we describe a Phase 1b/2 study to investigate the safety and antitumor activity of a chemotherapy-free combination of zanidatamab plus ALX148 in advanced HER2-expressing cancers, including breast cancer. Methods: ZWI-ZW25-204 is a Phase 1b/2, 2-part, open-label, multicenter study to evaluate the safety and antitumor activity of zanidatamab administered in combination with ALX148 in patients with locally advanced/inoperable and/or metastatic HER2-expressing cancer. Part 1 of this study will evaluate safety and tolerability and will establish the recommended doses (RDs) of zanidatamab plus ALX148. It will include patients with either HER2-positive (defined per ASCO/CAP guidelines) or HER2-low (defined as immunohistochemistry [IHC] 1+ or IHC 2+/in situ hybridization (ISH) negative) breast cancer. Part 2 will evaluate the antitumor activity of zanidatamab plus ALX148 (at their combination therapy RDs) in 3 expansion cohorts: HER2-positive breast cancer (Cohort 1), HER2-low breast cancer (Cohort 2) and other HER2-overexpressing advanced malignancies (Cohort 3). Other key eligibility criteria include: prior use of approved agents known to confer clinical benefit, disease progression on or after the most recent systemic therapy, measurable disease per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1). Patients will receive zanidatamab and ALX148, each administered intravenously once every 2 weeks in a 28-day treatment cycle. Response assessments will be performed every 8 weeks. Primary endpoints include safety and tolerability assessments (Part 1) and confirmed objective response rate per RECIST 1.1 (Part 2). Secondary endpoints in Part 2 include disease control rate, clinical benefit rate, duration of response, progression-free survival, overall survival, safety, pharmacokinetics, and immunogenicity assessments. The study is currently open for enrollment in the United States and may enroll up to 93 patients (NCT: 05027139). Citation Format: Sara A. Hurvitz, Jorge Chaves, Adam Brufsky, Alberto J. Montero, Bruno Fang, Kay Yeung, Manish R. Patel, Ritesh Parajuli, Adam Omidpanah, Elaina Gartner, Abraham Fong, Sophia Randolph, Funda Meric-Bernstam. Zanidatamab in combination with ALX148 in advanced human epidermal growth factor receptor 2 (HER2)-expressing cancers, including breast cancer: A phase 1b/2, multicenter, open-label, dose-finding and cohort-expansion study (ZWI-ZW25-204) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT1-14-01.

Background: Triple-negative breast cancer (TNBC) is an aggressive breast cancer subtype with a higher risk of locoregional and distance recurrence. Consequently, this population was considered poor candidate for breast conservation (BCT). Our study aim was to determine whether BCT plus radiotherapy (RT) was equivalent to mastectomy for TNBC after adjustment of selection bias of demographic and clinical characteristics. Methods: The National Cancer Database was queried for women diagnosed as primary unilateral invasive clinical T1-2N0-2 TNBC from 2004-2016. Patients who underwent mastectomy or breast conservation (partial mastectomy plus radiation) were included. A 1:1 propensity match with replacement was performed to compare breast conservation vs. mastectomy. Overall survival was analyzed using stratified multivariable Cox proportional hazard regression analysis.Results: Of 59,599 clinical T1-2N0-2 TNBC patients, 26,325 (44.2%) underwent mastectomy and 33,274 (55.8%) were treated with BCT. BCT patients were older (median age 59 vs. 54, p Citation Format: Lifen Cao, Christopher W Towe, Megan E Miller, Alberto J Montero, Robert Shenk. Breast conservation plus radiotherapy provides superior survival benefit than mastectomy in triple negative breast cancer: A propensity matched national cancer database analysis [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-18-02.

There is a male predominance of acute myeloid leukemia (AML) incidence, but survival data are conflicting. The objective of this study is to carry out a comprehensive analysis of sex differences in AML, and to investigate the impact of sex disparities in survival.The cohort included patients ≥18 years diagnosed with AML (2010-2022). Demographics, treatment patterns, treatment adverse events, and survival were analyzed. The population was described and compared by sex, and sex-based risks and associations were obtained via Cox proportional-hazards regression.In total, 1020 AML patients were analyzed (57.4% males), with lower risk of death for females (aHR = 0.41, 95% CI 0.26-0.66). Among females, BMT (aHR = 0.51, 95% CI 0.27-0.97), hospitalization record (aHR = 0.65, 95%CI 0.45-0.93), and higher appointment completion rates (aHR = 0.98, 95% CI 0.98-0.98) were associated with lower risk of death. Overall, and similarly in males, higher age at diagnosis (aHR = 1.03, 95% CI 1.02-1.04) and a TP53 mutation (aHR = 2.24, 95% CI 1.69-2.97) were associated with higher risk of death.Sex differences exist in both AML incidence and overall survival. Treatment and health care factors should be addressed by caregivers and public policies developed to reduce mortality rates and mitigate existing sex differences.

Background: Hormone receptor positive (HR+)/human epidermal growth factor receptor 2 negative (Her2-) breast cancers represent the majority of metastatic breast cancers (mBC) among women and are often treated with sequential courses of endocrine therapy (ET) prior to the eventual need for chemotherapy (CT). Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) block cell cycle progression and decrease proliferation of breast cancer cells. Currently, there are three available CDK4/6i: palbociclib, ribociclib and abemaciclib. Each has been shown to improve progression-free survival (PFS) when given with ET in the frontline setting, compared to ET alone. After progression on CDK4/6i, no standard of care exists for the next line of systemic therapy, and there are no prospective data to help guide clinical practice. Analysis of real-world data may provide insight into optimal second-line treatment for women who have progressed on CDK4/6i therapy. Methods: The nationwide Flatiron Health electronic health record-derived de-identified database was utilized for this analysis. We evaluated patient data collected from 2015-2020 for women with HR+/Her2- mBC who received CDK4/6i as frontline therapy and received a documented second-line systemic therapy. The objectives of this study were to describe what therapies were given as second-line treatment and estimate the real-world PFS (rwPFS) of those therapies. rwPFS was defined as time between initiation of second-line therapy until clinician-recorded progression (or death). Patients (pts) who did not progress or die were considered censored at the end of follow-up or end of second-line therapy. Results: A total of 1,210 pts with HR+/Her2- mBC received CDK4/6i with ET in the frontline setting, including 29.1% with de novo metastatic disease. Average age at diagnosis of metastatic disease was 64.4 years (range 28-84). A majority of pts received palbociclib in the frontline setting (88.2%), and 68.8% received an aromatase inhibitor (AI) as the frontline ET partner. 839 pts subsequently received second-line therapy (Table 1). CDK4/6i was continued as part of second-line treatment in 308 (36.7%) pts. 249 (29.7%) pts received CT as second-line treatment. The proportion of pts who continued CDK4/6i increased from years 2015-2020 (p=0.035), and the proportion who received CT decreased over time (p TABLE 1. Second-Line Therapy Used. F, fulvestrant; T, tamoxifenSECOND-LINE THERAPYOverall (N=839)AI23 (2.7%)CDK4/6i4 (0.5%)CDK4/6i + AI97 (11.6%)CDK4/6i + F160 (19.1%)CDK4/6i + F + AI35 (4.2%)CDK4/6i + F + T3 (0.4%)CDK4/6i + T3 (0.4%)CT249 (29.7%)F70 (8.3%)F + AI14 (1.7%)mTOR99 (11.7%)PARP4 (0.5%)PI3K16 (1.9%)T11 (1.3%)Clinical Trial51 (6.1%) Citation Format: James M Martin, Elizabeth A Handorf, Alberto J Montero, Lori J Goldstein. Analysis of systemic therapies following progression on frontline CDK4/6-inhibitor therapy [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS10-15.

Background. Given the significant clinical activity of the anti-PD1 inhibitor pembrolizumab as either a single agent or in combination with cytotoxic chemotherapy in the treatment of patients with metastatic triple-negative breast cancer (mTNBC), as well as the favorable cytotoxic and immunomodulatory properties of carboplatin and nab-paclitaxel, we identified a strong rationale to treat patients with mTNBC with the combination of carboplatin (C), nab-paclitaxel (N) and pembrolizumab (P) (CNP). Material and Methods. We undertook a prospective, single-arm pilot study of 30 patients with mTNBC treated at two institutions. Inclusion criteria included: radiographically measurable mTNBC, ECOG performance status of 0-1, Conclusions. CNP demonstrated significant activity in patients with mTNBC. Studies are underway to identify pathologic and genomic correlates of clinical response to CNP. Citation Format: Joseph Baar, Jame Abraham, G. Thomas Budd, Paula Silverman, Alberto Montero, Halle Moore, Pingfu Fu, Vinay Varadan, Kara Ladaika, Lauren Hricik. Pilot study of carboplatin, nab-paclitaxel and pembrolizumab for metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS12-16.

Background: Everolimus in combination with exemestane (EVE+EXE) was initially FDA approved to treat metastatic hormone receptor-positive breast cancer (mHRBC) in patients previously treated with nonsteroidal aromatase inhibitors based on the BOLERO-2 trial. However, none of the patients in the BOLERO-2 trial received prior CDK4/6 inhibitors, which have become standard of care for mHRBC. There is limited data to support the use and clinical benefit of EVE+EXE in mHRBC patients previously treated with CDK4/6 inhibitors. Methods: We reviewed patients ≥18 years old with mHRBC treated with EVE+EXE at our institution from January 1, 2012, to April 1, 2020. Patients were excluded if they received EVE+EXE ≤30 days. Data collected included patient and tumor characteristics, prior therapies in the metastatic setting, adverse drug events, and clinical outcomes. The primary objective was to compare progression free survival (PFS) for EVE+EXE between patients with and without prior exposure to CDK4/6 inhibitors. Secondary outcomes included overall survival (OS) and safety. Group comparisons were performed by two-sample t test or Wilcoxon rank sum test for continuous variables and Pearson’s chi-square test or Fisher’s exact test for categorical variables. Log-rank test was used to compare the PFS and OS between groups. Results: One-hundred ninety two patients were included in the study; 79 patients had received prior CDK4/6 inhibitor based therapies, while 113 patients did not. Baseline patient characteristics such as histology, menopause status, de novo metastatic disease, presence of lung or liver metastases, and bone only disease were similar between groups. There was a median of 2 lines of treatment in the metastatic setting prior to receiving EVE+EXE in both groups. Fewer patients received prior chemotherapy in the metastatic setting in those who received prior CDK4/6 inhibitors (32.9% vs 49.6%, p=0.032). In patients who received a prior CDK4/6 inhibitor, median PFS was 3.9 months (95% CI: 3.5 to 4.8) compared to 5.5 months (95% CI: 4.0 to 6.3) in those who did not receive a prior CDK4/6 inhibitor (HR for progression, 1.46; 95% CI: 1.08 to 1.97, p=0.013). Overall survival between groups was not significantly different. A total of 32 (16.7%) patients discontinued EVE+EXE due to intolerance or adverse drug events. Conclusion: Patients who received a prior CDK4/6 inhibitor had a lower median PFS benefit from EVE+EXE compared to those who did not. Citation Format: Hanjie Mo, Catherine E Renna, Halle CF Moore, Jame Abraham, Megan L Kruse, Alberto J Montero, Susan B LeGrand, G Thomas Budd. Efficacy of everolimus and exemestane for the treatment of metastatic hormone receptor-positive breast cancer in patients previously treated with CDK4/6 inhibitors [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS12-18.

Background: In patients (pts) with ER+/HER2− metastatic breast cancer (MBC) following progression on prior endocrine and CDK4/6i therapy, the EMERALD trial demonstrated significantly prolonged progression-free survival (PFS) and a manageable safety profile for elacestrant versus standard of care endocrine therapy (SoC). Benefit was observed in all pts and in pts with ESR1 mutant MBC (ESR1-mut). EMERALD is the only oral SERD monotherapy pivotal trial where all pts were pretreated with CDK4/6 inhibitor (CDK 4/6i). Here, we examine the impact of duration of prior CDK4/6i on PFS. Methods: EMERALD (NCT03778931) is a randomized, open-label, phase 3 trial that enrolled pts with ER+/HER2- MBC who previously had 1-2 lines of endocrine therapy, mandatory CDK4/6i, and ≤1 chemotherapy; prior treatment with fulvestrant was allowed. Patients were randomized 1:1 to elacestrant (400 mg orally daily) or SoC (investigator’s choice of aromatase inhibitor or fulvestrant). If randomized to the control arm, patients who received prior fulvestrant were to receive an aromatase inhibitor, and vice versa. If two CDK4/6i were used in the metastatic setting (n=40), the cumulative duration was calculated. Results: A total of 478 pts were randomized (228 with ESR1-mut) between Feb 2019 – Oct 2020 (n=239, elacestrant; n=239, SoC). Overall survival was not yet mature, as of September 2nd 2022. Updated PFS results show statistically significant results in favor of elacestrant, both in all pts and in pts with ESR1-mut. The duration of prior CDK4/6i in the metastatic setting was positively associated with PFS, the longer the duration of prior CDK4/6i in the metastatic setting (n=465), the longer the PFS on elacestrant versus SoC (Table 1). Updated safety data were consistent with previously reported results. Most of the adverse events (AEs), including nausea, were grade 1 and 2, and only 3.4% and 0.9% of the pts discontinued trial therapy because of an AE on elacestrant and SoC, respectively. A low percentage of pts received an antiemetic; 8.0%, 3.7%, and 10.3%, on elacestrant, fulvestrant, and AI, respectively. No hematological safety signal was observed and none of the patients in either of the two treatment arms had sinus bradycardia. Conclusions: EMERALD is the first phase 3 trial to demonstrate a significant PFS improvement versus SoC in all pts and in the subgroup with ESR1 mutations in pts with ER-positive/HER2-negative MBC with 1-2 prior lines of endocrine treatment ± one line of chemotherapy. Elacestrant demonstrated longer PFS versus SOC that was positively associated with the duration of prior treatment with CDK4/6i, which was more pronounced in pts with ESR1-mut MBC. In this 2nd and 3rd line setting, elacestrant was well tolerated with significantly longer PFS versus SoC, highlighting its potential role as a therapeutic option for pts with ER+/HER2- MBC. Table 1: PFS estimates in the elacestrant and SoC arms based on different cut-off points for the duration of prior CDK4/6i. Citation Format: Aditya Bardia, Francois-Clement Bidard, Patrick Neven, Guillermo Streich, Alberto J. Montero, Frederic Forget, Marie-Ange Mouret-Reynier, Joo Hyuk Sohn, Donatienne Taylor, Kathleen K. Harnden, Hung Khong, Judit Kocsis, Florence Dalenc, Patrick Dillon, Sunil Babu, Simon Waters, Ines Deleu, Jose Angel García-Sáenz, Emilio Bria, Marina Elena Cazzaniga, Philippe Aftimos, Javier Cortés, Giulia Tonini, Tarek Sahmoud, Nassir Habboubi, Krzysztof Grzegorzewski, Virginia Kaklamani. GS3-01 EMERALD phase 3 trial of elacestrant versus standard of care endocrine therapy in patients with ER+/HER2- metastatic breast cancer: Updated results by duration of prior CDK4/6i in metastatic setting [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS3-01.

PURPOSE Patients with pretreated estrogen receptor (ER)–positive/human epidermal growth factor receptor 2 (HER2)–negative advanced breast cancer have poor prognosis. Elacestrant is a novel, oral selective ER degrader that demonstrated activity in early studies. METHODS This randomized, open-label, phase III trial enrolled patients with ER-positive/HER2-negative advanced breast cancer who had one-two lines of endocrine therapy, required pretreatment with a cyclin-dependent kinase 4/6 inhibitor, and ≤ 1 chemotherapy. Patients were randomly assigned to elacestrant 400 mg orally once daily or standard-of-care (SOC) endocrine monotherapy. Primary end points were progression-free survival (PFS) by blinded independent central review in all patients and patients with detectable ESR1 mutations. RESULTS Patients were randomly assigned to elacestrant (n = 239) or SOC (n = 238). ESR1 mutation was detected in 47.8% of patients, and 43.4% received two prior endocrine therapies. PFS was prolonged in all patients (hazard ratio = 0.70; 95% CI, 0.55 to 0.88; P = .002) and patients with ESR1 mutation (hazard ratio = 0.55; 95% CI, 0.39 to 0.77; P = .0005). Treatment-related grade 3/4 adverse events occurred in 7.2% receiving elacestrant and 3.1% receiving SOC. Treatment-related adverse events leading to treatment discontinuations were 3.4% in the elacestrant arm versus 0.9% in SOC. Nausea of any grade occurred in 35.0% receiving elacestrant and 18.8% receiving SOC (grade 3/4, 2.5% and 0.9%, respectively). CONCLUSION Elacestrant is the first oral selective ER degrader demonstrating a significant PFS improvement versus SOC both in the overall population and in patients with ESR1 mutations with manageable safety in a phase III trial for patients with ER-positive/HER2-negative advanced breast cancer.

Human epidermal growth factor receptor 2 (HER2) is overexpressed in approximately 20% of all breast cancers. Before the development of HER2-directed monoclonal antibodies, HER2-positive breast cancer was associated with a rather poor prognosis. With the advent of monoclonal HER2-targeting antibodies (trastuzumab and pertuzumab) and antibody-drug conjugates (trastuzumab emtansine [T-DM1] and trastuzumab deruxtecan), clinical outcomes for HER2-positive breast cancer have dramatically changed, and a greater proportion of patients in the nonmetastatic setting are cured. However, in the metastatic setting, resistance to anti-HER2 treatments still remains a major therapeutic challenge, underscoring the importance of developing novel HER2-directed therapies. Over the last year, there has been a dramatic shift in the current treatment paradigms for HER2-positive metastatic breast cancer, with recent U.S. Food and Drug Administration approvals of trastuzumab deruxtecan (DS-8201), neratinib, and tucatinib in combination with trastuzumab and capecitabine. The authors summarize recent phase 3 data with novel HER2-targeted therapies as well as phase 1 and 2 data with other novel HER2-targeting agents.

Background: Invasive lobular breast cancer (ILC) is the second most common histological type of invasive breast cancer and accounts for 10-15% of all breast cancer cases. It is commonly strongly hormone receptor positive and, in general, is considered to be less chemo-sensitive compared with invasive ductal carcinoma (IDC). The aim of this study was to compare survival outcomes among ILC patients treated with adjuvant endocrine therapy (ET) compared with chemoendocrine therapy (CET). We also sought to assess utilization of Oncotype Dx testing and distribution of Recurrence Score results among ILC patients treated at our institution. Methods: We conducted an IRB approved retrospective study at Cleveland Clinic Taussig Cancer Institute of patients with non-metastatic ILC. Patient diagnosed with ILC and treated from January 2004 through December 2017 were identified from our tumor registry. Patient characteristics including demographics, pathologic features, hormone replacement therapy (HRT) use, Oncotype Dx recurrence score, treatment details and recurrence data were obtained through medical chart review. Recurrence-free and overall survival (OS) were compared between ET and CET using Kaplan-Meier method and Cox proportional hazard model with consideration of differences on age and prognostic factors. The outcomes between age and pathological stage propensity score matched treatment groups were also compared. Results: A total of 638 patients (Mean age 61.9±11.7, 99.1% estrogen receptor positive, 82.6% progesterone receptor positive) were identified. 406 (63.6%) patients received ET and 232 (36.4%) patients received CET. Compared to ET, patients who received CET were significantly younger (Mean 56.3 vs 65.0 years) and more likely to be premenopausal (40.1% vs 14.6%), however they had significant worse prognostic features including pathological stage (stage III: 38.9% vs 2.1%), grade (≥ II: 69.0% vs 55.9%) and Oncotype Dx score (≥18: 72.4% vs 36.2%). Patients were followed for median (IQR) time of 4 (2.0, 6.4) years for survival outcomes. Although recurrence-free survival (local or distant) was worse in CET (5-year recurrence-free: 81.9% vs 96.5%), age and clinical prognostic features adjusted recurrence risk was similar as ET (Adjusted HR and 95% CI: 0.83, 0.36-1.92) and risk of death was also similar (Adjusted HR and 95% CI: 0.68, 0.31-1.50). Only 222 patients had Oncotype Dx score (35%), with 59% falling in the low risk range, 39% intermediate risk range and 2% high risk range. The Oncotype Dx recurrence score was not associated with recurrence or death. The recurrence-free (5-year: 97.4% vs 90.4%, p=0.37) and OS (At 5-year OS: 94.3% vs 89.4%, p=0.08) were also similar between age and pathological stage matched CET and ET groups. Conclusion: Use of chemoendocrine therapy did not result in improved survival outcomes for patients with ILC compared to those treated with endocrine monotherapy in the adjuvant setting. The majority of ILC patients did not have Oncotype Dx testing sent however when it was ordered, most cases resulted in the low-intermediate risk range, suggesting limited benefit of chemotherapy as reflected by survival outcome results observed. Citation Format: Mathew Thomas, Hong Li, Jame Abraham, Halle CF Moore, G Thomas Budd, Alberto J Montero, Megan L Kruse. Comparison of survival outcomes between treatment with endocrine therapy and chemoendocrine therapy in patients with invasive lobular carcinoma [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-14-13.

Background: IDO1 is a mediator of tumor immune suppression through alteration of tryptophan metabolism. Indoximod (1-methyl-tryptophan) is an IDO1 pathway inhibitor. There is preclinical evidence that indoximod acts synergistically with chemotherapy such as taxanes (Uyttenhove, 2003) in an immune dependent fashion. Previous studies demonstrated the safety and activity of indoximod combined with docetaxel in patients with advanced solid tumors, including breast cancer (Soliman, 2014). A phase 2 clinical trial was designed to study the efficacy of indoximod plus taxanes in metastatic breast cancer (MBC) patients (pts). Method: This is a phase II randomized, 1:1 placebo controlled clinical trial, that enrolled MBC pts in multiple centers in the US and Poland. Eligibility criteria included ER+ or ER- HER2- MBC, ability to receive taxane therapy, PS 0-1, normal organ function and absence of autoimmune disease. Pts were randomized to taxane (either weekly paclitaxel 80mg/m2 3 on 1 off or q3wk docetaxel at 75mg/m2 per treating physician’s discretion) + placebo (TP) or taxane + indoximod 1200mg PO BID (TI) as first line treatment for MBC. Primary endpoint was PFS. The sample size of 154 patients was designed to detect a HR of .64 with one sided α=.1 and β=.2 after 95 events. Archival tumor tissue was stained with IHC for IDO1 expression when available. Aperio digital pathology positive pixel algorithm was used for scoring, with manual verification. Median value was used as cut-off for IDO positivity. Results: 164 pts were randomized and treated (85 TI, 79 TP). Demographics and tumor features are shown in table 1. Treatment discontinuation was due to disease progression (60%), adverse events (10%), other (30%). Objective response rate was 40% in TI and 37% in TP arm (p=.74). The median PFS was 6.0 (95% CI, 4.5, 8.1) months in the TI arm and 8.4 (95% CI, 5.6, 9.8) in the TP arm, HR of 1.14 (0.81, 1.60). The median OS was 21.6 months (CI 95%, 16, 39.1) in the TI arm and 21.2 (CI 95%, 19.1, 32.1) in the TP arm. The median follow up was 17.4 (range 0.1, 39.4) months. Grade ≥3 treatment emergent adverse events were observed in 60% of patients in both arms with neutropenia, fatigue, anemia, diarrhea being most common but not significantly different between arms. An exploratory analysis of IDO staining with outcomes in 42 samples (22 in TI and 20 TP) suggested a difference in median PFS in pts with high IDO expression assigned to TI vs. TP (10.3 vs 4 months, p=.047). No other prognostic or predictive associations were observed based on IDO status in the analysis. Conclusions: The combination of indoximod with a taxane in 1st line HER2- MBC was safe and did not result in added toxicity. In an unselected population, no improvement in clinical outcomes was observed for the combination over taxane alone. However, higher tumor IDO expression may select for MBC pts who benefit more from indoximod and should be investigated as a predictive biomarker in future studies. Demographics and tumor featuresIndoximodPlaceboOverallParameterStatistic(N=85)(N=79)(N=164)Age (years)n8579164median (min, max)58 (29,76)57 (29,85)58 (29,85)GenderMalen (%)1 (1.2)2 (2.5)3 (1.8)Femalen (%)84 (98.8)77 (97.5)161 (98.2)RaceWhiten (%)71 (83.5)66 (83.5)137 (83.5)African Americann (%)12 (14.1)10 (12.7)22 (13.4)Asiann (%)1 (1.2)01 (0.6)Othern (%)1 (1.2)3 (3.8)4 (2.4)ECOG status0n (%)41 (48.8)43 (54.4)84 (51.5)1n (%)44 (52.2)36 (44.3)80 (46.6)Hormone Receptor StatusNegativen (%)23 (27.1)23 (29.1)46 (28.0)Positiven (%)62 (72.9)56 (70.9)118 (72.0)Choice of TaxaneDocetaxeln (%)62 (72.9)59 (74.7)121 (73.8)Paclitaxeln (%)23 (27.1)20 (25.3)43 (26.2) Citation Format: Veronica Mariotti, Shou-Ching Tang, Patrick Dillon, Alberto Montero, Andrew Poklepovic, Susan Melin, Ibrahim Nuhad, Petros Nikolinakos, Eugene Kennedy, Hyo Han, Roohi Ismail-Khan, Daniel Bruetman, Oana Danciu, Paul Gilman, Boguslawa Karaszewska, Krzysztof Lesniewski-Kmak, Timothy Panella, Dhimant Patel, Malgorzata Suszko-Kazarnowicz, Fabio Volterra, Hatem Soliman. Results of a phase II double-blinded, randomized, placebo-controlled clinical trial of Indoximod, an Indoleamine-2,3-dioxygenase 1 (IDO1) inhibitor, in combination with Taxane chemotherapy in metastatic breast cancer (MBC) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr PD1-04.

Purpose: Approximately 20% of all breast cancers (BC) are HER2 amplified. In the APT trial, weekly paclitaxel/ trastuzumab in node negative HER2+ BC with tumors Methods: In the National Cancer Database (2004-2017), patients with a primary diagnosis of pT1N0M0 HER2+ BC, were separated into two groups: (i) HER2 monotherapy, i.e. trastuzumab, and (ii) chemo-HER2 therapy. A 3:1 propensity match was performed to balance patient selection bias between the two different cohorts. Long-term overall survival (OS) was compared between both groups. Results: A total of 23, 281 patients met the criteria. 22,268 (96.7%) received chemo-HER2 therapy and 1,013 (4.4%) received HER2 monotherapy. Propensity match identified 1,995 patients who received chemo-HER2 therapy, and 666 who received HER2 monotherapy. After match, adjuvant chemo-HER2 therapy was associated with a modest survival advantage over HER2 monotherapy (5-year OS 94.1% vs. 90.6%, P=0.041). Conclusions: Even though there is a modest OS advantage favoring adjuvant chemo-HER2 therapy in pT1N0 HER2+ BC, HER2 monotherapy was associated with 5-year OS >90%. Therefore, in select patients who have contraindications for cytotoxic chemotherapy, or decline adjuvant chemotherapy, adjuvant trastuzumab monotherapy appears to be a reasonable alternative.

Background: Routine sentinel lymph node biopsy (SLNB) has been recommended against by Choosing Wisely© Foundation due to its low value in clinical node negative, hormone receptor positive breast cancer patients age≥70 years old. We used the National Cancer Database (NCDB) to examine the effect of SLNB omission and outcomes in this population. We hypothesized that SLNB would be beneficial in this population.Methods: The National Cancer Database was queried for women diagnosed with primary unilateral invasive clinical stage T1N0M0 hormone receptor positive, HER-2 negative breast cancer from 2012-2017. Patients age ≥ 70 years old with Charlson Score ≥1 who underwent partial mastectomy and received hormonal therapy were included in the study cohort. Patients received neoadjuvant therapy or underwent upfront axillary lymph node dissection (ALND) were excluded. A 1:3 propensity match with replacement was performed to compare SLNB omission vs. SLNB group controlling age, race, comorbidities, insurance and facility. Overall survival was analyzed using stratified multivariable Cox proportional hazard regression analysis.Results: Of 14,150 patients, 1,928 (13.6%) omitted SLNB and 12,222 (86.4%) underwent SLNB, including 1,545/12,222 (12.6%) who proceeded to ALND. Central portion tumor location (OR=1.77, P=0.001), clinical T1c (OR= 2.49, P Citation Format: Lifen Cao, Megan E Miller, Luke D Rothermel, Alberto J Montero, Christopher W Towe, Robert Shenk. Less is not necessarily more: A propensity matched national analysis on effect and outcome of sentinel lymph node biopsy omission [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr PD7-08.

Real-world data are critical to demonstrate the reproducibility of evidence and external generalizability of randomized clinical trials. Palbociclib is an oral small-molecule inhibitor of cyclin-dependent kinases 4 and 6 that has been shown to improve progression-free survival (PFS) when combined with letrozole or fulvestrant in phase 3 clinical trials. We evaluated real-world outcomes in metastatic breast cancer patients who received palbociclib in combination with endocrine therapy in routine clinical practice. Records of patients with advanced hormone receptor (HR)-positive breast cancer treated with palbociclib at the Cleveland Clinic health system from February, 2015 to December, 2017 were retrospectively reviewed. The primary end point was PFS. In this cohort, 411 women were included. The median age and follow-up times were 53.5 years and 10.2 months, respectively. The median PFS for palbociclib plus letrozole was 15.1 months for patients treated in first line, 10.5 months in second line, and 4.2 months in third line and beyond. For patients who received fulvestrant plus palbociclib, the median PFS in first, second, and third line and beyond were 11.6, 12.3, and 6.4 months, respectively. The most common adverse events were hematologic, with grade 3–4 neutropenia occurring in 58% of patients. Thirty-one (8%) patients permanently discontinued palbociclib due to adverse events. Among patients with HR-positive advanced breast cancer, the estimated PFS in patients treated with fulvestrant and palbociclib was comparable to a previously reported phase 3 trial. However, the median PFS with letrozole and palbociclib was shorter than previously reported data from phase 2 and 3 trials. Palbociclib toxicity was very manageable, with a low drug discontinuation rate.

Background gpNMB is an internalizable transmembrane protein overexpressed in ˜40% of TNBC, and associated with a worse prognosis. Preclinical data implicates gpNMB in tumor invasion and metastasis. GV is a novel ADC designed to deliver monomethyl auristatin E (MMAE) to gpNMB-overexpressing cells. Prior phase 1/2 studies suggested promising activity of GV in gpNMB-overexpressing TNBC. Methods In the METRIC trial (NCT#01997333), patients (pts) with mTNBC were randomized 2:1 to GV (1.88 mg/kg IV q21 days) or capecitabine (2,500 mg/m2 PO daily d1-14 q21 days) until disease progression or intolerance. Key eligibility criteria included: gpNMB over-expression (>25% tumor cells positive by central immunohistochemistry of archival tissue); estrogen and progesterone receptor expression Results From Feb 2014 to Aug 2017, 327 women were randomized at 120 institutions to GV (n=218) or capecitabine (n=109). Pretreatment characteristics were well balanced between arms: median age of 55 years; 77% visceral disease; 2.4 years median duration of disease at study entry; 1 median prior anticancer regimen for metastatic disease. At the cut-off for final data analysis (Nov 30, 2017), 21 pts remained on treatment and 98 pts were alive. For GV vs. capecitabine based on independent central review, median PFS was 2.9 (95% CI: 2.8, 3.5) vs. 2.8 (95% CI: 1.6, 3.2) months (HR=0.95; p=0.76); median OS was 8.9 (95% CI: 7.9, 10.5) vs. 8.7 (95% CI: 6.9, 10.8) months (HR=1.06; p=0.73); ORR was 16% (95% CI: 11.1, 22.4) vs. 15% (95% CI: 8.6, 23.5); and median DOR was 5.6 (95% CI: 3.0, 7.8) vs. 4.2 (95% CI: 3.0, 12.2) months. A post-hoc subgroup analysis suggested the greatest benefit from GV was in potentially taxane-sensitive disease (i.e., not previously rechallenged or >6 months progression-free interval following last taxane). The incidence of grade ≥ 3 treatment-related adverse events (TRAEs) was 58% in the GV arm and 37% in the capecitabine arm. The most common grade ≥ 3 TRAEs were neutropenia (27%), rash (15%), and leukopenia (9%) in the GV arm, and diarrhea (14%) and palmar-plantar erythryodysesthesia (8%) in the capecitabine arm. There was 1 fatal TRAE of neutropenic sepsis in the GV arm and none in the capecitabine arm. Conclusion The METRIC study evaluating GV in mTNBC did not meet the primary efficacy endpoint of improved PFS over capecitabine. While anticancer activity was seen with GV, it was comparable to capecitabine with no therapeutic advantage of GV in terms of ORR, PFS, or OS. The safety profile of GV was consistent with prior experience with no new safety signals identified. Citation Format: Vahdat LT, Forero-Torres A, Schmid P, Blackwell K, Telli ML, Melisko M, Holgado E, Moebus V, Cortes J, Fehrenbacher L, Montero AJ, Ma C, Nanda R, Wright GS, He Y, Bagley RG, Halim A, Turner CD, Yardley DA. METRIC: A randomized international phase 2b study of the antibody-drug conjugate (ADC) glembatumumab vedotin (GV) in gpNMB-overexpressing, metastatic, triple-negative breast cancer (mTNBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-20-01.

543 Background: Early validation studies using the Oncotype DX recurrence score (RS) in NSABP B20 demonstrated that women with node negative breast cancer and RS >31 had significant survival benefit from the addition of adjuvant chemotherapy to endocrine therapy (CET). Consequently, in the prospective TAILORx trial, node negative women with RS >26 received CET. These studies did not clearly delineate the magnitude of benefit of adjuvant chemotherapy for post-menopausal node negative women. A recently published well-designed adjuvant trial (RxPONDER) demonstrated that adjuvant chemotherapy was not beneficial in post-menopausal pts with ER+/HER2- breast cancer, 1-3 positive nodes, and RS 26 compared to endocrine therapy (ET) alone, given that CET is more beneficial in women 50 with ER+/HER2- pT1-2N0M0 breast cancer with RS >26, to assess real world utilization. We separated women into two groups based on adjuvant treatment: ET alone or CET. Chi-square and logistic regression analysis determined difference between different systemic treatment groups. OS was analyzed using a multivariable Cox model. Results: A total of 16,745 eligible women who underwent surgery and received ET were identified in the NCDB—4,740 (28.3%) received ET alone and 12,005 (71.7%) received CET. We observed that CET use increased over time. Women were more likely to receive CET if their tumors were moderately differentiated (OR = 1.853, p < 0.001), poorly/undifferentiated tumors (OR = 3.875, p < 0.001), or associated with lymph-vascular invasion (OR = 1.206, p = 0.001). After accounting for demographic and oncologic factors, 5-year OS rates in this cohort were significantly superior in women receiving CET compared to ET alone (95.4% vs 92.0%, Hazard Ratio = 0.680, p < 0.001). Conclusions: Utilizing the NCDB to represent real world outcomes, we observed that women > 50 years with pT1-2N0M0 ER+/HER2- breast cancer, and RS > 26 had a significantly superior 5-year OS when receiving adjuvant chemotherapy provides a measurable OS benefit for post-menopausal women in this setting and should be discussed with patients.

1100 Background: EMERALD demonstrated significantly prolonged progression-free survival (PFS) and a manageable toxicity profile for elacestrant vs standard of care endocrine therapy (SOC) in patients with ER+/HER2- mBC following progression on prior endocrine and CDK4/6 inhibitor therapy. Benefit was observed in the overall study population and in patients with ESR1 mutations (mESR1). Here, we report a subgroup analysis from EMERALD in patients with no prior chemotherapy. Methods: EMERALD (NCT03778931) is a randomized, open-label, phase 3 trial that enrolled patients with ER+/HER2− mBC who had 1–2 lines of endocrine therapy, mandatory pretreatment with a CDK4/6 inhibitor, and ≤1 chemotherapy. Patients were randomized 1:1 to elacestrant (400 mg orally daily) or SOC (investigator’s choice of fulvestrant or aromatase inhibitor). Primary endpoints were PFS in all patients and patients with mESR1. In this analysis, we compared PFS between elacestrant and SOC in patients without prior chemotherapy. Results: Among the 477 patients enrolled in the trial, 77.8% (n = 371) had not received prior chemotherapy for mBC (median age = 64). Among patients without prior chemotherapy, treatment with elacestrant was associated with significantly prolonged PFS compared to SOC in both the overall population (hazard ratio [HR] = 0.68 [95% CI, 0.52-0.89] P = 0.004; median PFS 3.7 vs 2.0; 6-mo PFS 38% vs 23%; 12-mo PFS 27% vs 12%), and patients with mESR1 (HR = 0.54 [95% CI, 0.36-0.80] P = 0.002; median PFS 5.3 vs 1.9; 6-mo PFS 44% vs 24%; 12-mo PFS 31% vs 12%). Key treatment-related adverse events (AEs) in the no prior chemotherapy elacestrant group were nausea (25.9%), fatigue (12.7%), and hot flush (11.1%). There were no treatment-related deaths in either group. Conclusions: Among patients with ER+/HER2− mBC without prior chemotherapy, elacestrant significantly prolonged PFS compared to SOC endocrine therapy and showed favorable outcomes in this subgroup. Clinical trial information: NCT03778931.

540 Background: Based on the results of the RxPonder trial, post-menopausal women over age 50 with estrogen receptor (ER)+ breast cancer, 1-3+ nodes, and a 21-gene Oncotype DX recurrence score (RS) score of 20 being associated with a significantly inferior overall survival (OS) (P value range: < 0.001-0.019). In women with RS of 20-25, CET was associated with a significant improvement in OS compared to ET alone, regardless of age (age < = 50: HR = 0.334, P = 0.002; age > 50: HR = 0.521, P = 0.019). Conclusions: Among women with ER+/HER2- breast cancer with 1–3 positive nodes, and RS of 20-25, in contrast to the RxPonder trial we observed that CET was associated with an OS benefit in women regardless of age.

TPS10618 Background: Coronavirus disease 2019 (COVID-19), caused by betacoronavirus SARS-CoV-2, is associated with an increased risk of severe infection or death in cancer patients compared to the general population. The CANVAX trial recently demonstrated that short term immune responses to SARS-CoV-2 vaccines are modestly impaired in patients with cancer— particularly those who receive myelosuppressive chemotherapy. Because little is known regarding longitudinal antibody or T-cell responses in cancer patients who receive cytotoxic chemotherapy or non-myelosuppressive targeted systemic therapy, the aim of this longitudinal study is to assess immune B and T cell responses to SARS-CoV-2 over a 12-month period in solid tumor patients who receive chemotherapy or non-immunosuppressive therapy compared to healthy individuals without cancer. Methods: This is an ongoing prospective non-interventional clinical trial (NCT05238467). Approximately 100 patients will be enrolled into three different arms. Accrual began in May 2021 and 37 patients have been enrolled. Eligible patients must not have prior COVID-19 infection < 6 months from study enrollment and have a diagnosis of a solid tumor (breast, genitourinary, or gastrointestinal cancers), who either: received myelosuppressive chemotherapy within 60 days prior to initial or booster COVID vaccination, or who started on chemotherapy within 30 to 60 days after the initial or booster COVID vaccination (Arm A); or received non-immunosuppressive treatments (Arm B); or have no history of cancer or prior history of cancer but beyond 12 months from completion of curative cancer treatment (Arm C, control cohort). Whole blood will be collected in accordance with standard operating procedures. Blood samples analyzed for the presence of antibodies against the major antigenic components of SARS-CoV-2 including the spike glycoprotein (S), receptor binding domain (R) and nucleocapsid phosphoprotein (N). Antibody levels will be quantified utilizing quantitative ELISA. T-cell responses will also be quantified. The primary endpoint is seroprotection rate with an antibody titer protective (1:40) at any point: baseline, 2, 6, and 12 months. The secondary endpoint is to evaluate differences in longitudinal immunological responses to SARS-CoV-2 over a 12-month period. The difference of the seroprotection rate among 3 cohorts of participants will be examined using chi-square test. Moreover, the effect of treatment (chemotherapy, endocrine, TKIs) on seroprotection will be estimated using multivariable logistic regression controlling the effects of confounders, such as age, gender and cancer type. COVID antibody titers measured over time (baseline, 8 weeks, 6, 9, 12 months after the second vaccination) will be analyzed using mixed-effect models. Clinical trial information: NCT05238467.

Background Radiotherapy is the recommended treatment after breast‐conserving surgery (BCS) for early‐stage breast cancer (BC). However, there is no clear evidence whether radiotherapy after BCS improves the survival of elderly women diagnosed with early‐stage hormone receptor‐positive (HR+) BC. The aim of this study was to investigate the survival benefit associated with radiotherapy plus hormonal therapy vs hormonal therapy alone after BCS for early‐stage HR+ BC patients. Methods Using the Surveillance, Epidemiology, and End Results linked with Medicare data, we identified elderly (65 years and older) women diagnosed with early‐stage HR+ BC (2006‐2011) who received hormonal therapy with or without radiotherapy after BCS. A log‐rank test, Cox proportional hazards models, and propensity score matching were used to estimate the overall survival (OS) benefit associated with radiotherapy after BCS. Results Of the 5688 patients, there were 303 deaths from any cause. One hundred and eighty‐five (61%) of these deaths occurred in the hormonal therapy group, and 118 (39%) deaths occurred in the radiotherapy plus hormonal therapy group. The mean survival time in the radiotherapy plus hormonal therapy group was 5.32 ± 1.86 years compared with 4.92 ± 1.86 years in the hormonal therapy group. Based on the adjusted and propensity score matching analysis, patients in the adjuvant radiotherapy group had a lower risk of death compared with those who did not receive radiotherapy. Radiotherapy plus hormonal therapy decreased the risk of death by 32%. The effect estimates were similar in the adjusted and matched cohorts. Conclusions Radiotherapy plus hormonal therapy resulted in a significant improvement in the OS of elderly women diagnosed with HR+ BC.

Importance Indoleamine 2,3-dioxygenase 1 (IDO1) causes tumor immune suppression. The IDO1 pathway inhibitor indoximod combined with a taxane in patients with ERBB2-negative metastatic breast cancer was tested in a prospective clinical trial. Objective To assess clinical outcomes in patients with ERBB2-negative metastatic breast cancer treated with indoximod plus a taxane. Design, setting, and participants This phase 2 double-blinded randomized 1:1 placebo-controlled clinical trial enrolled patients at multiple international centers from August 26, 2013, to January 25, 2016. Eligibility criteria included ERBB2-negative metastatic breast cancer, ability to receive taxane therapy, good performance status, normal organ function, no previous immunotherapy use, and no autoimmune disease. The study was discontinued in June 2017 because of lack of efficacy. Data analysis was performed from February 2019 to April 2020. Interventions A taxane (paclitaxel [80 mg/m2] weekly 3 weeks on, 1 week off, or docetaxel [75 mg/m2] every 3 weeks) plus placebo or indoximod (1200 mg) orally twice daily as first-line treatment. Main outcomes and measures The primary end point was progression-free survival (PFS); secondary end points were median overall survival, objective response rate, and toxic effects. A sample size of 154 patients would detect a hazard ratio of 0.64 with 1-sided α = .1 and β = .2 after 95 events. Archival tumor tissue was stained with immunohistochemistry for IDO1 expression as an exploratory analysis. Results Of 209 patients enrolled, 169 were randomized and 164 were treated (85 in the indoximod arm; 79 in the placebo arm). The median (range) age was 58 (29-85) years; 166 (98.2%) were female, and 135 (79.9%) were White. The objective response rate was 40% and 37%, respectively (indoximod vs placebo) (P = .74). The median (range) follow-up time was 17.4 (0.1-39.4) months. The median PFS was 6.8 months (95% CI, 4.8-8.9) in the indoximod arm and 9.5 months (95% CI, 7.8-11.2) in the placebo arm (hazard ratio, 1.2; 95% CI, 0.8-1.8). Differences between the experimental and placebo arms in median PFS (6.8 vs 9.5 months) and overall survival (19.5 vs 20.6 months) were not statistically significant. Grade 3 or greater treatment-emergent adverse events occurred in 60% of patients in both arms. Conclusions and relevance This randomized clinical trial found that, among patients with ERBB2-negative metastatic breast cancer, addition of indoximod to a taxane did not improve PFS compared with a taxane alone. Trial registration ClinicalTrials.gov Identifier: NCT01792050.

BACKGROUND: Interleukin-12 (IL-12) is a potent immunoregulatory cytokine that plays a key role in the crosstalk between innate (dendritic, macrophage, and natural killer) and adaptive (T and B) cells promoting anti-tumor immune responses. DNA plasmid-based IL-12 delivered to accessible tumors by intratumoral injection and electroporation (TAVO-EP) has been shown to induce activation of innate and adaptive tumor-infiltrating and peripheral immune cells, regression of treated and distant untreated lesions (abscopal effect), and expression of PD-L1 in patients with melanoma or triple-negative breast cancer (TNBC), without the systemic toxicity that has limited therapeutic use of IL-12 historically. The combination of TAVO-EP and pembrolizumab has demonstrated durable responses in melanoma patients with immunologically “cold” tumors or with prior progression on anti-PD1 therapy. Early clinical data indicate similar potential for eliciting strengthened immunogenic responses in TNBC. KEYNOTE-890 (OMS-I141) is a Phase 2 study in patients with metastatic TNBC to evaluate the safety and efficacy of TAVO-EP + pembrolizumab in the second-line or later (2L+) treatment setting (Cohort 1) or TAVO-EP + pembrolizumab + chemotherapy in the first-line (1L) setting (Cohort 2). Cohort 1 data are presented in a separate abstract. Enrollment in Cohort 2 is ongoing. METHODS: Cohort 2 of this Phase 2, open-label, multicenter study will be assessing the safety and efficacy of TAVO-EP in combination with pembrolizumab and chemotherapy as a first-line treatment for metastatic TNBC. Eligible patients are adults with metastatic TNBC (ER and PR staining Citation Format: Melinda Telli, Bianca Devitt, Katharine Cuff, Shaveta Vinayak, Rita Nanda, Alberto J. Montero, Rina Hui, David A. Canton, Christopher Twitty, Sunny Xie, Donna Bannavong, Bridget O'Keeffe, Sandra Aung, Rohit Joshi. Trial in progress: Phase 2 study of intratumoral plasmid interleukin-12 (tavokinogene telseplasmid; TAVO™) plus electroporation in combination with pembrolizumab with or without chemotherapy in patients with inoperable locally advanced or metastatic triple-negative breast cancer (KEYNOTE-890/OMS-I141) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr OT2-01-03.

Background: Endocrine therapy(ET) plus CDK4/6 inhibitor (i) is the mainstay for the management of estrogenreceptor-positive (ER+)/HER2- mBC. However, most patients (pts) with ER+ mBCeventually experience disease progression, including development of ESR1mutations (mESR1). Elacestrant, an oral SERD, demonstrated preclinical activity,and clinical activity in a phase 1 trial in ER+ mBC, including responses in ptswith prior fulvestrant, CDK4/6i, and mESR1tumors (Bardia JCO 2021).. Methods: EMERALD(NCT03778931), a multicenter, international, randomized, open-label, controlledphase 3 trial, enrolled postmenopausal pts with ER+/HER2- mBC who had received 1-2prior lines of ET and ≤1 line of chemotherapy in the mBC setting and had prior progressionon a ET plus CDK4/6i. Pts were randomized 1:1 to elacestrant (400 mg orallydaily) or standard of care (SOC; investigator’s choice of fulvestrant or anaromatase inhibitor). Stratification factors included mESR1 status (by central lab), priorfulvestrant exposure, and presence of visceral disease. The study had 2 primary endpoints of progression-free survival (PFS), by blindedindependent review committee, in pts withtumors harboring mESR1 and in all pts (mESR1 or mESR1 notdetected). Secondary endpoints included: overall survival (OS), safety, tolerability,and quality of life. An alpha-value of 0.0475 was used to determine statisticalsignificance (2-sided using the truncated Hochberg procedure).. Results: EMERALD enrolled 477 pts(228 with mESR1) between Feb 2019 - Oct 2020, with 239 pts randomized toreceive elacestrant vs 238 pts to SOC. Demographics and disease characteristicswere well-balanced across treatment arms [median age: 63 yrs vs 63.5 yrs; 2prior lines: 46% vs 40.8%; prior CDK4/6i: 100% in both arms]. The study met bothprimary endpoints. There was a 30% reduction in the risk of progression ordeath in the elacestrant arm in all pts (HR=0.697 [95% CI: 0.552, 0.88]; P=0.0018),and a 45% (HR=0.546 [95% CI: 0.387, 0.768]; P=0.0005) reduction in therisk of progression or death in pts with mESR1.For both endpoints, results in key prespecified subgroups, including visceral metastases,number of prior lines of therapy, pretreatment with fulvestrant, and geographicalregion, were consistent with the overall outcome. The PFS rate at 12 months was 22.32% (95% CI: 15.24%, 29.40%)with elacestrant vs 9.42% (95% CI: 4.02%, 14.81%) with SOC in all pts, and26.76% (95% CI: 16.17%, 37.36%) vs 8.19% (95% CI: 1.26%, 15.12%) in the mESR1 subgroup. The prespecified interim OS analysis plannedat the time of the final PFS analysis (allocated2-sided alpha level of 0.0001) demonstrated a trend in favor of elacestrant inall pts (HR=0.751 [95% CI: 0.542, 1.038]; P=0.0821) and in pts with mESR1(HR=0.592 [95% CI: 0.361, 0.958]; P=0.0325). The final OS analysisis expected next year. Common (>10%) treatment-related adverse events (AEs) withelacestrant vs SOC included: nausea (25.3% vs 8.7%), vomiting (11% vs 2.6%), and fatigue (11% vs 7.9%), mostlygrade 1/2. Treatment-emergent AEs leading to discontinuation of elacestrant orSOC were infrequent in both arms (6.3% and 4.4%). Grade ≥3 treatment-relatedAEs in the elacestrant arm vs SOC were 7.2% vs 3.1%, mainly driven by nausea(2.1% vs 0.9%). There were no treatment-related deaths in either group.. Conclusions:Elacestrant is the first oral SERD to demonstrate a statistically significantand clinically meaningful improvement of PFS vs SOC in a randomized phase 3study in pts with ER+/HER2- mBC in the 2nd/3rd-linesetting, including those whose tumors harbor mESR1. Elacestrant was well tolerated and hasthe potential to become the new standard of care for pts with ER+/HER2- mBC. Citation Format: Aditya Bardia, Patrick Neven, Guillermo Streich, Alberto J. Montero, Frédéric Forget, Marie-Ange Mouret-Reynier, Joo Hyuk Sohn, Peter Vuylsteke, Kathleen K. Harnden, Hung Khong, Judit Kocsis, Florence Dalenc, Virginia Kaklamani, Patrick Dillon, Sunil Babu, Simon Waters, Ines Deleu, José García-Sáenz, Emilio Bria, Marina Cazzaniga, Janice Lu, Philippe Aftimos, Javier Cortes, Shubin Liu, Dirk Laurent, Maureen G. Conlan, Francois-Clement Bidard. Elacestrant, an oral selective estrogen receptor degrader (SERD), vs investigator’s choice of endocrine monotherapy for ER+/HER2- advanced/metastatic breast cancer (mBC) following progression on prior endocrine and CDK4/6 inhibitor therapy: Results of EMERALD phase 3 trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS2-02.

Background CDK4/6 inhibitors (CDK4/6i), in combination with aromatase inhibitors, are United States Food and Drug Administration-approved for the treatment of hormone receptor-positive (HR+)/human epidermal growth factor receptor 2-negative (HER2−) metastatic breast cancer (MBC). The effectiveness of continuing them beyond first disease progression (PD) is currently unknown. This retrospective study evaluated the impact of the continuation of CDK4/6i beyond first PD in HR+/HER2− MBC using real-world experience. Patients and Methods A single-institution retrospective review of patients with HR+ MBC who received CDK4/6is from 2015 to 2018 and where CDK4/6is were continued beyond first PD. The primary outcome was progression-free survival (PFS) after initial PD on CDK4/6i therapy. Results Thirty women with HR+/HER2− MBC met eligibility criteria. Patients were identified from a prospective database of patients at the Cleveland Clinic Foundation who were prescribed CDK4/6is. The median age and follow-up duration were 47.5 years and 27 months, respectively. Most patients received palbociclib (PA)/letrozole as initial therapy (67%), followed by PA/fulvestrant (23%), and PA/other aromatase inhibitor (20%), and abemaciclib with either fulvestrant or letrozole (6%). As of January 31, 2019, 25 (83.3%) patients were still alive, and 19 (63%) patients had progressed. The estimated median PFS for continued CDK4/6i use beyond the first PD was 11.8 months (95% confidence interval, 5.34-13.13 months). Conclusions Among a small cohort of patients with HR+ MBC in a non-clinical trial setting, continuation of CDK4/6i-endocrine treatment post initial PD was associated with a median PFS of about 12 months. Formal randomized clinical trials evaluating the continuation of CDK4/6is beyond the first PD are currently ongoing and will provide more answers to this important clinical question.

584 Background: Approximately 30% of all breast cancers are characterized as triple-negative (TNBC). TNBC typically occurs in younger women and is associated with a poorer prognosis relative to other breast cancer subtypes. High levels of tumor-infiltrating lymphocytes (TILs) in residual disease after Neoadjuvant chemotherapy (NACT) have previously been shown to be associated with better prognosis in TNBC. In this work, we sought to evaluate the prognostic value of computationally derived measures of TIL spatial architecture in residual TNBC after NACT. Methods: H&E-stained samples from 92 patients (pts) with TNBC (41 died, 45 had disease recurrence) and residual disease after NACT were retrospectively collected from 2 sites: Instituto Nacional de Enfermedades Neoplásicas (S1) and University Hospitals (S2). 45 pts (16 deaths, 23 recurrences) from S1 formed the training set and 47 pts (25 deaths, 22 recurrences) from S2 formed the independent validation cohort. Samples were digitized at 20x. Computerized algorithms automatically identified 2 types of nuclei (TILs and non-TILs) and built clusters for each nuclei type based on cell proximity. The spatial arrangement of these clusters was then quantified using network graph metrics. The top 5 features, determined by least absolute shrinkage and selection operator, were used to train a Cox regression model that assigned a risk of death and recurrence to each patient on the training set. The percentile 33 risk score was used as a threshold for stratifying pts on the validation set as either low or high risk. For comparison, we also employed a model based on TIL density alone. Survival analysis was used to evaluate the performance of both approaches on disease-free survival (DFS) and overall survival (OS). Results: Pts in S2 (n=47) identified as “high risk” by the model based on spatial architecture of residual TILs had a significantly shorter survival time. The median OS for pts at high risk was 25 months vs. 55 months for low-risk pts. The median DFS for pts at high risk was 32 months vs 51 months for low-risk pts. Univariable analysis showed this model was prognostic for both OS (Hazard Ratio (HR) = 2.57, 95% Confidence Interval (CI): 1.07-6.16, p=0.03) and DFS (HR=2.38, CI: 1.01-5.62, p=0.04). In contrast, the model based on TIL density was not prognostic for OS (HR=1.24, CI: 0.33-4.63, p=0.73) nor DFS (HR=1.19, CI: 0.32-4.34, p=0.78). Conclusions: A computerized image analysis model based on measurements of spatial arrangement of residual TILs and surrounding cells was found to be prognostic in TNBC pts who received NACT. This method appears to be more prognostic than TIL density alone. Additional multisite validation and multivariable analysis is needed to further establish the independent prognostic utility of TIL based image biomarkers in the post-NACT TNBC.

In 1996, Jim Allison demonstrated that blocking the immune regulatory molecule CTLA-4 with anit-CTLA4 antibody led to enhance tumor responses in mice. It would take an additional 15 years for human studies to confirm the potency and clinical efficacy of anti-CTLA4, ultimately leading to US FDA approval of the first checkpoint inhibitor, ipilimumab. Now with a plethora of immune-modulating agents demonstrating single agent safety and benefit across many tumor types, investigation on the optimal combination of immune-based therapies has begun in earnest. While there are many challenges, a central one is how to select which combination for which patient is the best. Here we review the current approaches that a practitioner can use to achieve this therapeutic goal.

Genomic profiling can identify targetable mutations; however, the impact of tissue-based genomic profiling on clinical decision making for patients with metastatic breast cancer has not been well characterized. Patients with stage IV breast cancer who had undergone genomic profiling between 7/2013 and 3/2015 were identified at three academic cancer centers. Genomic analysis was determined to have impacted clinical decision if (A) a patient was enrolled onto a genotype-matched clinical trial or (B) prescribed off-label an FDA-approved therapy targeting an identified mutation. The frequency of mutated genes was determined. A total of 117 patients with stage IV breast cancer were identified. Median age was 46 (25–75). Fifty-three patients (45%) had ER-positive/HER2-negative disease, 50 (43%) had ER-negative/HER2-negative disease, and 14 (12%) had ER-any/HER2-positive disease. Median number of previous therapies received prior to genomic profiling was 2 (range 0–15), and median follow-up after testing was obtained after 5.8 months (range 0–24.4 months). Commercial reports indicated that 85 (73%) patients had at least one mutation targetable by an FDA-approved medication, and 112 (96%) patients had at least one clinical trial available; however, clinical management was only affected in 11 patients (9%). The most frequent mutations observed were those in TP53, FGF, PI3KCA, MYC, ZNF, FGFR, CCND, ARID1A, GATA3, and MAP; frequencies of these mutations varied by clinical subtype. Tumor genomic profiling affected clinical management in a minority of patients with metastatic breast cancer, thus these data do not support the routine use of genomic profiling outside of a clinical trial.

Purpose Patients who are diagnosed with stage IV metastatic melanoma have an estimated 5-year relative survival rate of only 17%. Randomized controlled trials of recent US Food and Drug Administration–approved immune checkpoint inhibitors—pembrolizumab (PEM), nivolumab (NIVO), and ipilumumab (IPI)—demonstrate improved patient outcomes, but the optimal treatment sequence in patients with BRAF wild-type metastatic melanoma remains unclear. To inform policy makers about the value of these treatments, we developed a Markov model to compare the cost-effectiveness of different strategies for sequencing novel agents for the treatment of advanced melanoma. Materials and Methods We developed Markov models by using a US-payer perspective and lifetime horizon to estimate costs (2016 US$) and quality-adjusted life years (QALYs) for treatment sequences with first-line NIVO, IPI, NIVO + IPI, PEM every 2 weeks, and PEM every 3 weeks. Health states were defined for initial treatment, first and second progression, and death. Rates for drug discontinuation, frequency of adverse events, disease progression, and death obtained from randomized phase III trials were used to determine the likelihood of transition between states. Deterministic and probabilistic sensitivity analyses were conducted to evaluate model uncertainty. Results PEM every 3 weeks followed by second-line IPI was both more effective and less costly than dacarbazine followed by IPI then NIVO, or IPI followed by NIVO. Compared with the first-line dacarbazine treatment strategy, NIVO followed by IPI produced an incremental cost effectiveness ratio of $90,871/QALY, and first-line NIVO + IPI followed by carboplatin plus paclitaxel chemotherapy produced an incremental cost effectiveness ratio of $198,867/QALY. Conclusion For patients with treatment-naive BRAF wild-type advanced melanoma, first-line PEM every 3 weeks followed by second-line IPI or first-line NIVO followed by second-line IPI are the most cost-effective, immune-based treatment strategies for metastatic melanoma.

Optimal ex vivo expansion protocols for adoptive cell therapy (ACT) must yield T cells able to effectively home to tumors and survive the inhospitable conditions of the tumor microenvironment (TME), while simultaneously exerting persistent anti-tumor effector functions. Our previous work has shown that ex vivo activation in the presence of IL-12 can induce optimal expansion of murine CD8(+) T cells, thus resulting in significant tumor regression after ACT mostly via sustained secretion of IFN-γ. In this report we further elucidate the mechanism of this potency, showing that IL-12 additionally counteracts the negative regulatory effects of autocrine IFN-γ. IL-12 not only downregulates PD-1 expression by T cells, thus minimizing the effects of IFN-γ-induced PD-L1 upregulation by tumor stromal cells, but also inhibits IFNγR2 expression, thereby protecting T cells from IFN-γ-induced cell death. Thus, the enhanced anti-tumor activity of CD8(+) T cells expanded ex vivo in the presence of IL-12 is due not only to the ability of IL-12-stimulated cells to secrete sustained levels of IFN-γ, but also to the additional capacity of IL-12 to counter the negative regulatory effects of autocrine IFN-γ.

Based on available phase III trial data, we performed a cost-effectiveness analysis of different treatment strategies that can be used in patients with newly diagnosed HER2-positive metastatic breast cancer (mBC).We constructed a Markov model to assess the cost-effectiveness of four different HER2 targeted treatment sequences in patients with HER2-positive mBC treated in the U.S. The model followed patients weekly over their remaining life expectancies. Health states considered were progression-free survival (PFS) 1st to 3rd lines, and death. Transitional probabilities were based on published phase III trials. Cost data (2015 US dollars) were captured from the U.S. Centers for Medicare and Medicaid Services (CMS) drug payment table and physician fee schedule. Health utility data were extracted from published studies. The outcomes considered were PFS, OS, costs, QALYs, the incremental cost per QALY gained ratio, and the net monetary benefit. Deterministic and probabilistic sensitivity analyses assessed the uncertainty around key model parameters and their joint impact on the base-case results.The combination of trastuzumab, pertuzumab, and docetaxel (THP) as first-line therapy, trastuzumab emtansine (T-DM1) as second-line therapy, and lapatinib/capecitabine third-line resulted in 1.81 QALYs, at a cost of $335,231.35. The combination of trastuzumab/docetaxel as first line without subsequent T-DM1 or pertuzumab yielded 1.41 QALYs, at a cost of $175,240.69. The least clinically effective sequence (1.27 QALYs), but most cost-effective at a total cost of $149,250.19, was trastuzumab/docetaxel as first-line therapy, T-DM1 as second-line therapy, and trastuzumab/lapatinib as third-line therapy.Our results suggest that THP as first-line therapy, followed by T-DM1 as second-line therapy, would require at least a 50 % reduction in the total drug acquisition cost for it to be considered a cost-effective strategy.

Background: Indoleamine 2,3 dioxygenase (IDO) is a tryptophan-catabolizing enzyme that plays a key role in the normal regulation of peripheral immune tolerance. Tumors also employ this mechanism to induce a state of immunosuppression, evading immune mediated destruction. Indoximod (D-1-methyltryptophan) is a broad IDO pathway inhibitor as it has been shown to potentially interfere with multiple targets within the IDO pathway. Preclinical studies in MMTV-neu mouse models have demonstrated that combining indoximod with cytotoxic chemotherapy had a greater in-vivo anti-tumor effect than either agent alone. A phase 1 trial combining docetaxel and indoximod demonstrated safety and responses in metastatic breast cancer (mBC) patients. Based on these data a phase 2 trial evaluating indoximod in combination with taxane chemotherapy as first line therapy in patients with metastatic breast cancer was initiated. Methods: The study is a 1:1 randomized, placebo controlled, four arm phase 2 trial. The study treatment is docetaxel 75mg/m2 IV D8 plus indoximod 1200mg PO BID D1-14 every 21 days or matching placebo in study arms 1A and 2A or paclitaxel 80 mg/m2 IV weekly 3 out of 4 weeks with indoximod or matching placebo given BID Days 1-14 in arms 1B and 2B. The primary endpoint is progression free survival. Secondary endpoints include overall survival, response rate, safety, and immune response correlative assays. Patients with measurable, histologically confirmed mBC, no prior chemotherapies (hormonal therapies allowed) in the metastatic setting, ER+ or ER –, HER2 -, ECOG PS 0-1, no active CNS disease, no active autoimmune disease are eligible. Target enrollment is 154 patients. Results: At submission, 65 patients have evaluable safety data on trial. The pooled, blinded data was evaluated for any safety signals. Patient demographics include median age 58 years, 95% female, 17% African American, 25% triple-negative disease, and 82% with multiple sites of metastatic disease. 28% of patients had at least one Grade 3 or 4 adverse event. Those occurring in multiple patients include dyspnea 5%, pleural effusion 3%, non-cardiac chest pain 3%, and febrile neutropenia 3%. Most patients had at least one adverse event (86%). The most common were anemia 14%, tearing 11%, constipation 19%, diarrhea34%, nausea 44%, vomiting 22%, fatigue 48%, peripheral edema 17%, increased liver function tests 10%, lymphopenia 17%, hyperglycemia 15%, myalgia 14%, dizziness 14%, dysguesia 16%, headache 20%, peripheral neuropathy 12%, dyspnea 19%, alopecia 34%, and rash 14%, all compatible with the side effect profile of single agent taxanes. No immune specific serious advents were reported. No treatment related deaths have been reported. Conclusion: The aggregate safety data for these 65 patient are similar to what is typically observed with docetaxel and paclitaxel. No unexpected serious immune linked adverse events were reported. The trial is currently open at multiple clinical sites in the US and Europe and actively enrolling patients. Updated data will be presented. NCT01191216. Citation Format: Tang S-C, Montero A, Munn D, Link C, Vahanian N, Kennedy E, Soliman H. A phase 2 randomized trial of the IDO pathway inhibitor indoximod in combination with taxane based chemotherapy for metastatic breast cancer: Preliminary data. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P2-11-09.

7057 Background: Cancer patients (pts) are at high risk of unplanned hospital readmissions. Predicting which cancer patients are at higher risk of readmission would improve post-discharge follow-up/navigation, decrease cost, and improve pt outcomes. Methods: We conducted a retrospective cohort study of non-surgical cancer pts hospitalized at our center between 12/2014 to 7/2018. A machine learning algorithm was trained on 348 medical, sociodemographic and cancer-specific variables with a total of 1,801,944 data points. The cohort was randomly divided into training (80%) and validation (20%) subsets. Prediction performance was measured by area under the receiver operator characteristic curve (AUC). Results: A total of 5,178 hospitalizations were included, of which 45.1% were women, and 27.6% experienced an unplanned readmission within 30 days. The most frequently represented cancers were hematologic malignancies (30.5%), followed by GI (18.1%), lung (13.7%), and GU (10.9%). Significant variables that impacted the algorithm decision are ranked from the most to the least important, including: days from last admission; planned index chemotherapy admission; number of vascular access lines, drains, and airways in use; length of stay; cancer diagnosis; total ED visits in past 6 months; age; discharge lab values (sodium, albumin, alkaline phosphatase, bilirubin, platelets); number of prior admissions; and discharge disposition. The AUC for the validation subset was 0.80. To ease the translation of this model into the clinic, we developed a web application whereby users can supply the aforementioned variables to the model and receive a personalized prediction that highlights those variables most affecting a subject’s readmission risk status: www.Cancer-Readmission.com. Conclusions: A cancer-specific readmission risk model with high AUC for 30-days unplanned readmission has been developed. The model is embedded in a freely available web application that provides personalized, patient-specific predictions. Programs that integrate this model can identify cancer patients with a greater risk for unplanned hospital readmission, thus providing a personalized approach to prevent future unplanned readmissions.

Breast cancer is a global health concern. In fact, breast cancer is the primary cause of death among women worldwide and constitutes the most expensive malignancy to treat. As health care resources are finite, decisions regarding the adoption and coverage of breast cancer treatments are increasingly being based on "value for money," i.e., cost-effectiveness. As the evidence about the cost-effectiveness of breast cancer treatments is abundant, therefore difficult to navigate, systematic reviews of published systematic reviews offer the advantage of bringing together the results of separate systematic reviews in a single report. As a consequence, this paper presents an overview of systematic reviews of the cost-effectiveness of hormone therapy, chemotherapy, and targeted therapy for breast cancer to inform policy and reimbursement decision-making. A systematic review was conducted of published systematic reviews documenting cost-effectiveness analyses of breast cancer treatments from 2000 to 2014. Systematic reviews identified through a literature search of health and economic databases were independently assessed against inclusion and exclusion criteria. Systematic reviews of original evaluations were included only if they targeted breast cancer patients and specific breast cancer treatments (hormone therapy, chemotherapy, and targeted therapy only), documented incremental cost-effectiveness ratios, and were reported in the English language. The search strategy used a combination of these key words: "breast cancer," "systematic review/meta-analysis," and "cost-effectiveness/economics." Data were extracted using predefined extraction forms and qualitatively appraised using the assessment of multiple systematic reviews (AMSTAR) tool. The literature search resulted in 511 bibliographic records, of which ten met our inclusion criteria. Five reviews were conducted in the early-stage breast cancer setting and five reviews in the metastatic setting. In early-stage breast cancer, evidence about trastuzumab value differed by age. Trastuzumab was cost-effective only in women with HER2-positive breast cancer younger than 65 years and over a life-time horizon. The cost-effectiveness of trastuzumab in HER2-positive metastatic breast cancer yielded conflicting results. The same conclusions were reached in comparisons between vinorelbine and taxanes. In both early stage and advanced/metastatic breast cancer, newer aromatase inhibitors (AIs) have proved cost-effective compared to older treatments. This overview of systematic reviews shows that there is heterogeneity in the evidence concerning the cost-effectiveness of hormone therapy, chemotherapy, and targeted therapy for breast cancer. The cost-effectiveness of these treatments depends not only on the comparators but the context, i.e., adjuvant or metastatic setting, subtype of patient population, and perspective adopted. Decisions involving the cost-effectiveness of breast cancer treatments could be made easier and more transparent by better harmonizing the reporting of economic evaluations assessing the value of these treatments.

Vitamin D (VD) supplementation has pleiotropic effects that extend beyond their impact on bone health, including the disruption of human epidermal growth factor receptor 2 (HER2) signaling through the ErbB2/AKT/ ERK pathway. We performed a retrospective review of patients who received VD supplementation during neoadjuvant chemotherapy (n [ 134) and those who did not (n [ 112). In our final multivariate model, VD use was associated with improved disease-free survival (DFS) (hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.15-0.88); P [ .026). To the best of our knowledge, our study is the first to report a significant improvement in DFS for patients who received VD supplementation concurrently with trastuzumab-based chemotherapy for HER2-positive (HER2 D ) nonmetastatic breast cancer. Background: Vitamin D (VD) supplementation has pleiotropic effects that extend beyond their impact on bone health, including the disruption of downstream VD receptor signaling and human epidermal growth factor receptor 2 (HER2) signaling through the ErbB2/AKT/ERK pathway. In the present study, we examined our institutional experience with patients having nonmetastatic HER2-positive (HER þ ) breast cancer and hypothesized that those patients who received VD supplementation during neoadjuvant chemotherapy would have improved long-term outcomes. Patients and Methods: We performed a retrospective review of all patients (n ¼ 308) given trastuzumab-based chemotherapy between 2006 and 2012 at the University of Miami/Sylvester Comprehensive Cancer Center (UM/SCCC). We identified 2 groups of patients for comparison—those who received VD supplementation during neoadjuvant chemotherapy (n ¼ 134) and those who did not (n ¼ 112). Univariate and multivariate Cox proportional hazard regression models were fitted to overall survival (OS) and disease-free survival (DFS). Results: More than half of the patients received VD during neoadjuvant chemotherapy (54.5%), with 60% receiving a dose < 10,000 units/wk and 33.3% having aV D deficiency at the start of therapy. In our final multivariate model, VD use was associated with improved DFS (hazard ratio [HR], 0.36; 95% confidence interval [CI], 0.15-0.88; P ¼ .026], whereas larger tumor size was associated with worse DFS (HR, 3.52; 95% CI, 1.06-11.66; P ¼ .04). There were no differences in OS based on any of

Background Glycoprotein NMB (gpNMB) is an internalizable transmembrane protein overexpressed in approximately 20% of breast cancer (BC), including approximately 40% of TNBC. gpNMB is a poor prognostic marker in BC (Rose CCR 2010) and preclinically has been implicated in tumor invasion, metastasis, and angiogenesis. GV is a novel antibody-drug conjugate targeting the potent cytotoxin monomethylauristatin E (MMAE) to gpNMB overexpressing cancer cells. In a Phase I/II study and the Phase II "EMERGE" study, GV demonstrated promising activity with TNBC patients (pts) deriving the greatest benefit and exhibiting the highest degree of gpNMB overexpression. GV was well-tolerated with the most frequent treatment-related toxicities consisting of rash, neutropenia, and neuropathy. In subset analyses of the EMERGE trial, objective response rate (ORR) was 30% (7/23) for GV vs. 9% (1/11) for investigator's choice in tumors with gpNMB overexpression (>25% of tumor epithelium); 18% (5/28) vs. 0% (0/11) in TNBC; and 40% (4/10) vs. 0% (0/6) in gpNMB-overexpressing TNBC for GV and IC respectively, with apparent improvements in progression-free survival (PFS; hazard ratio (HR) = 0.11) and overall survival (OS; HR = 0.14). Trial design The METRIC Trial (NCT#01997333) is an international (USA, CA, Aus), two-arm phase II study. Pts are randomized 2:1 to GV (1.88 mg/kg IV q 21 days) or capecitabine, a current standard of care for this population (2,500 mg/m2 daily for d1-14, q21 days) until progression or intolerance. Crossover is not permitted. Eligibility criteria Key eligibility criteria include: >25% of tumor epithelium gpNMB+ by central immunohistochemistry (IHC) screening of archival tissue; estrogen receptor and progesterone receptor 2 toxicity. Specific aims The primary endpoint is PFS per independent, blinded central review committee according to RECIST 1.1. Secondary endpoints are ORR, duration of response, OS, safety, pharmacokinetics and pharmacodynamics. Exploratory endpoints are quality of life and/or cancer-related pain. Statistical methods and target accrual The trial has 85% power to detect a PFS HR of 0.64 with two sided α = 0.05. The hypothesized median PFS is 4.0 months for capecitabine and 6.25 months for GV. Target accrual is open for 300 pts. Citation Format: Melisko M, Yardley DA, Blackwell K, Forero A, Ma C, Montero A, Daniel BR, Wright G, Fehrenbacher L, Chew H, Ferrario C, Nanda R, Seiler Jr M, Guthrie T, Vance K, Ouellette G, He Y, Bagley RG, Zhang J, Vahdat LT. The METRIC trial: A randomized international study of the antibody-drug conjugate glembatumumab vedotin (GV or CDX-011) in patients with metastatic gpNMB-overexpressing triple-negative breast cancer (TNBC). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr OT1-03-15.

To determine if a low fixed dosing strategy of capecitabine would produce comparable clinical activity with less adverse toxicities compared to published data with higher doses in the setting of metastatic breast cancer (mBC). We retrospectively analyzed patients treated with a low fixed dose of capecitabine (CAPE-L) at 1,000 mg twice daily for 14 days every 21 days. Outcomes included clinical benefit rate (CBR), overall response rates (ORR), time to progression (TTP), and overall survival (OS). A historical comparison group of mBC patients treated on 12 prior trials at the package-insert dose of capecitabine (n = 1,949) was utilized. Eighty-six patients were analyzed in our cohort. Positive hormone receptor status (79.1 vs. 50.6 %), and capecitabine as first-line chemotherapy (44.2 vs. 16.5 %) were more frequent in our cohort relative to the historical comparison. The median starting dose in our cohort was 633.5 mg/m(2). The CBR was similar between the CAPE-L and the standard dose cohorts (55.8 vs. 49.5 %), as was ORR (24.3 vs. 24 %), and median TTP (7 mo, 95 % CI 5.5-8.5 vs. 5.1 mo, 95 % CI 4.5-5.7). Median OS was longer in our cohort (24 mo, 95 % CI 16.8-31.2) than the historic standard dose cohort (12.1 mo, 95 % CI 9.6-14.4), a difference that was likely explained by the higher proportion of patients in the CAPE-L cohort who received capecitabine as first-line chemotherapy and who had hormone receptor positive disease. As expected, adverse events were less frequent with CAPE-L. We found that CAPE-L, which translates into a dose of 600-650 mg/m(2), appeared to have good clinical efficacy and acceptable toxicity.

64 Background: In the era of increasing therapeutic options and complexity of disease, some cancer patients (pts) continue aggressive treatment even within days of death. Previous studies report 30-66% of pts do not receive hospice or palliative services in the last month of life and many are enrolled in hospice < 3 days before death. Quality measures are endorsed by ASCO, National Quality Forum, and Oncology Care Model to increase hospice utilization. It is shown that pts enrolled in hospice have increased survival time with reduced in-hospital resources. These benefits increase the longer pts are in hospice. We hypothesize early identification of high risk pts by a multidisciplinary group and formulation of a care plan will prompt early discussion for hospice eligibility, increasing referrals to hospice and the number of days spent in hospice. Methods: As reported (ASCO 2018, Abst 6547), an Interdisciplinary Care Team (ICT) was created with palliative medicine and oncology physicians, nurses, and social workers. Twice monthly pts with high utilization over a 60-day period were identified. Care plans (CP) were created using a team based approach with parallel input from outpatient teams. CP was communicated back to the primary team. Results: 112 pts were discussed over 24 months; 39 pts died with a solid tumor malignancy and this was our study cohort. 85% pts (33/39) were referred to or had a hospice discussion and 82% pts (27/33) enrolled. 6 pts declined and 6 acutely died. Of the 27 pts that entered hospice 78% (21/27) were enrolled > 3 days and 22 % (6/27) < 3 days. Average number days in hospice was 19.7 (median 11) for all who entered hospice. In the subgroup that were enrolled for > 3 days, average number days was 25 (median 21). 62% pts (17/27) entered hospice within 60 days of ICT meeting and CP. Conclusions: Early identification of high-utilizing cancer patients along with review by ICT may correlate with early recognition of hospice eligibility, enrollment, and therefore greater number days spent in hospice. This increases hospice utilization allowing patients and families to experience the full benefit of hospice-directed care. Further interventions should be explored in optimizing transitions of care.

e18184 Background: Venous thromboembolism (VTE) complicates several anti-cancer regimens including chemotherapy and anti-angiogenic agents. Cyclin-dependent kinase 4/6 inhibitors (CDKIs) are a new approach for hormone receptor positive (HR+) metastatic breast cancer (mBC). Reported VTE rates in randomized trials range from 0.6% for ribociclib (MONALEESA-2) to 2% for palbociclib (PALOMA-3) and 5% for abemaciclib (MONARCH-3) but these may underestimate actual rates compared to patients in clinical practice who are generally older and have greater comorbidities. Little is known about real world incidence or prevalence of VTE with CDKIs in mBC. The aim of this study was to evaluate rates of VTE in clinical practice and association with outcomes in mBC patients on CDKIs. Methods: We conducted a retrospective cohort study at Cleveland Clinic Taussig Cancer Institute, approved by the institutional review board. We identified consecutive mBC patients who received any of three FDA-approved CDKIs (palbociclib, ribociclib, abemaciclib) from 1/2015 through 12/2017. VTE including deep venous thrombosis (DVT) and pulmonary embolism (PE) were identified by electronic medical record review. Overall survival (OS), progression free survival (PFS) and time to VTE were estimated by the Kaplan-Meier method and evaluated for association with VTE using Cox proportional hazard regression. Results: The study population included 424 patients, with a median age at diagnosis of 54.76 yrs, (range 27 -85). Palbociclib was the most commonly used CDKI (n = 390, 91.8%); 27 patients (6.3%) received more than one drug. VTE during CDKI therapy occurred in 9% of patients (n = 38), including DVT in 52.6% (n = 20), PE in 18.5% (n = 7) and visceral vein thrombosis (VVT) in 15.8% (n = 6). Median time to VTE was 314 days, and 6-months rate was 4.1%. VTE was associated with numerically worse PFS and OS, but this was not statistically significant (PFS [HR 1.25, 95% CI 0.73 – 2.14, p = 0.42], OS [HR 1.60, 95% CI 0.89 – 2.87, p = 0.12]). Conclusions: VTE affected nearly 10% of breast cancer patients receiving CDKIs, 2- to 5-fold greater than reported in registration trials. Further work is necessary to identify pathophysiology, risk factors and benefit of thromboprophylaxis.

e12515 Background: Women with stage IV HER2+ breast cancer typically have longer overall survival (OS) compared to other breast cancer subsets due to the effectiveness of dual anti HER-2 antibody therapy. The role of mastectomy remains controversial. Methods: We reviewed patients who were diagnosed with stage IV HER2+ breast cancer between 2/2015 and 12/2017 at Cleveland Clinic. Overall survival (OS) was estimated by the Kaplan-Meier method, and compared by the log-rank test. Univariable and multivariable analysis were performed using Cox regression to identify predictors of OS. Results: We identified 47 patients, with a median age of 58 (range: 22 – 87). Twenty-eight (60%) and 14 (30%) patients had ER+ and PR+ disease, respectively. Four patients had brain metastasis at time of stage IV diagnosis. All patients received systemic therapy. 17 (36%) patients underwent mastectomy after diagnosis of stage IV breast cancer,. Of the 30 (64%) patients who did not undergo mastectomy, 24 (80%), 2 (7%), and 4 (13%) were treated with both chemotherapy and HER2-directed therapy, chemotherapy alone, and HER2-directed therapy alone, respectively. Breast radiotherapy was performed on 9 (53%) and 8 (27%) patients in mastectomy and no mastectomy cohorts, respectively. Median follow-up time was 22 months . The two-year OS for mastectomy and no mastectomy cohorts were 94% (95% CI: 83 – 100) and 50% (95% CI: 33 – 76), respectively (p=0.009). On univariable analysis, only mastectomy vs no mastectomy (HR: 0.18, 95% CI: 0.04 – 0.80, p=0.025) predicted OS. On multivariable analysis, mastectomy vs no mastectomy has remained to be statistically significant predictor of OS (HR: 0.08, 95% CI: 0.01 – 0.66, p=0.019), whereas age, chemotherapy, HER2-directed therapy, and breast radiation were not independent predictors of improved OS (p>0.05). Conclusions: In our cohort, mastectomy was an independent predictor of longer OS in women with stage IV HER2+ breast cancer.

e12538 Background: CDK inhibitors (CDKi), in combination with aromatase inhibitors (AI), are approved for the treatment of hormone receptor positive (HR+) Her2 negative metastatic breast cancer (MBC). The effectiveness of continuing CDKi beyond first disease progression is not known. This study evaluated real world evidence and assessed the impact of continuation of CDKi beyond first disease progression in combination with endocrine therapy. Methods: This is a retrospective, single institution review of HR+ MBC patients treated with CDKi from 2015-2018 who continued CDKi after initial progression. The primary outcome was progression-free survival (PFS) beyond first disease progression, as assessed by the clinician based on radiological and/or clinical criteria. Overall survival (OS) – defined as date of initial CDKi treatment to date of death or last follow up – was a secondary outcome. Results: 30 women with HR+/HER2- MBC, median age 47.5 years (range: 31 – 81), sequentially continued on CDKi beyond first progression were identified from a database of patients treated with Palbociclib. Median and average follow up times on CDKi were 27.18 and 24.53 months, respectively. Initial endocrine/CDKi regimen received included: palbociclib (PA)/letrozole (LTZ) [67%], PA/fulvestrant (FULV) [23%], and PA/other AI [10%]. Prescribed combinations beyond 1st progression were: PA/FULV [56.7%], PA/LTZ [16.7%], and PA/other AI [20%], abemaciclib plus LTZ or FULV [6%]. As of 1/31/2019, 25 patients (83.3%) were still alive, and 19 (63%) had undergone a second progression on CDKi. The estimated median PFS for the entire duration while on CDKi was 23.5 months (95% CI 12.8 – 27.8), of which 11.8 months (95% CI 5.34 – 13.13) was the median PFS beyond first progression. The estimated median OS was 45.4 months. Conclusions: Among a small cohort of HR+ MBC patients, in a non-clinical trial setting, continuation of palbociclib plus endocrine therapy beyond first progression was associated with a median PFS of approximately 11 months. Formal clinical evaluation of continuation of CDK inhibitor plus endocrine therapy beyond first progression is warranted.