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Most invasive lobular breast cancers (ILC) are of the luminal A subtype and are strongly hormone receptor–positive. Yet, ILC is relatively resistant to tamoxifen and associated with inferior long-term outcomes compared with invasive ductal cancers (IDC). In this study, we sought to gain mechanistic insights into these clinical findings that are not explained by the genetic landscape of ILC and to identify strategies to improve patient outcomes. A comprehensive analysis of the epigenome of ILC in preclinical models and clinical samples showed that, compared with IDC, ILC harbored a distinct chromatin state linked to gained recruitment of FOXA1, a lineage-defining pioneer transcription factor. This resulted in an ILC-unique FOXA1–estrogen receptor (ER) axis that promoted the transcription of genes associated with tumor progression and poor outcomes. The ILC-unique FOXA1–ER axis led to retained ER chromatin binding after tamoxifen treatment, which facilitated tamoxifen resistance while remaining strongly dependent on ER signaling. Mechanistically, gained FOXA1 binding was associated with the autoinduction of FOXA1 in ILC through an ILC-unique FOXA1 binding site. Targeted silencing of this regulatory site resulted in the disruption of the feed-forward loop and growth inhibition in ILC. In summary, ILC is characterized by a unique chromatin state and FOXA1–ER axis that is associated with tumor progression, offering a novel mechanism of tamoxifen resistance. These results underscore the importance of conducting clinical trials dedicated to patients with ILC in order to optimize treatments in this breast cancer subtype. Significance: A unique FOXA1–ER axis in invasive lobular breast cancer promotes disease progression and tamoxifen resistance, highlighting a potential therapeutic avenue for clinical investigations dedicated to this disease. See related commentary by Blawski and Toska, p. 3668

Pattern of HER2 amplification in the subset of HER2 heterogeneous tumors. Heatmap generated using data from central pathology evaluation of HER2 heterogeneity. The graphic includes patients classified as HER2 heterogeneous depicted in each row. The color code to the right of the heatmap refers to the percentage of HER2 amplified cells per core biopsy tumor area. Core biopsy tumor areas, A, B and C were obtained from core biopsy site 1 and D, E and F from core biopsy site 2.

FISH raw counts

Intratumor heterogeneity is postulated to cause therapeutic resistance. To prospectively assess the impact of HER2 (ERBB2) heterogeneity on response to HER2-targeted therapy, we treated 164 patients with centrally confirmed HER2-positive early-stage breast cancer with neoadjuvant trastuzumab emtansine plus pertuzumab. HER2 heterogeneity was assessed on pretreatment biopsies from two locations of each tumor. HER2 heterogeneity, defined as an area with ERBB2 amplification in >5% but P < 0.0001, adjusted for hormone receptor status). Single-cell ERBB2 FISH analysis of cellular heterogeneity identified the fraction of ERBB2 nonamplified cells as a driver of therapeutic resistance. These data suggest HER2 heterogeneity is associated with resistance to HER2-targeted therapy and should be considered in efforts to optimize treatment strategies.Significance:HER2-targeted therapies improve cure rates in HER2-positive breast cancer, suggesting chemotherapy can be avoided in a subset of patients. We show that HER2 heterogeneity, particularly the fraction of ERBB2 nonamplified cancer cells, is a strong predictor of resistance to HER2 therapies and could potentially be used to optimize treatment selection.See related commentary by Okines and Turner, p. 2369.This article is highlighted in the In This Issue feature, p. 2355

PURPOSE Palbociclib is a cyclin-dependent kinase 4 and 6 inhibitor approved for advanced breast cancer. In the adjuvant setting, the potential value of adding palbociclib to endocrine therapy for hormone receptor–positive breast cancer has not been confirmed. PATIENTS AND METHODS In the prospective, randomized, phase III PALLAS trial, patients with hormone receptor–positive, human epidermal growth factor receptor 2–negative early breast cancer were randomly assigned to receive 2 years of palbociclib (125 mg orally once daily, days 1-21 of a 28-day cycle) with adjuvant endocrine therapy or adjuvant endocrine therapy alone (for at least 5 years). The primary end point of the study was invasive disease-free survival (iDFS); secondary end points were invasive breast cancer–free survival, distant recurrence-free survival, locoregional cancer-free survival, and overall survival. RESULTS Among 5,796 patients enrolled at 406 centers in 21 countries worldwide over 3 years, 5,761 were included in the intention-to-treat population. At the final protocol-defined analysis, at a median follow-up of 31 months, iDFS events occurred in 253 of 2,884 (8.8%) patients who received palbociclib plus endocrine therapy and in 263 of 2,877 (9.1%) patients who received endocrine therapy alone, with similar results between the two treatment groups (iDFS at 4 years: 84.2% v 84.5%; hazard ratio, 0.96; CI, 0.81 to 1.14; P = .65). No significant differences were observed for secondary time-to-event end points, and subgroup analyses did not show any differences by subgroup. There were no new safety signals for palbociclib in this trial. CONCLUSION At this final analysis of the PALLAS trial, the addition of adjuvant palbociclib to standard endocrine therapy did not improve outcomes over endocrine therapy alone in patients with early hormone receptor–positive breast cancer.

Supplementary Table from A Distinct Chromatin State Drives Therapeutic Resistance in Invasive Lobular Breast Cancer

Supplementary Figure from A Distinct Chromatin State Drives Therapeutic Resistance in Invasive Lobular Breast Cancer

Most invasive lobular breast cancers (ILC) are of the luminal A subtype and are strongly hormone receptor–positive. Yet, ILC is relatively resistant to tamoxifen and associated with inferior long-term outcomes compared with invasive ductal cancers (IDC). In this study, we sought to gain mechanistic insights into these clinical findings that are not explained by the genetic landscape of ILC and to identify strategies to improve patient outcomes. A comprehensive analysis of the epigenome of ILC in preclinical models and clinical samples showed that, compared with IDC, ILC harbored a distinct chromatin state linked to gained recruitment of FOXA1, a lineage-defining pioneer transcription factor. This resulted in an ILC-unique FOXA1–estrogen receptor (ER) axis that promoted the transcription of genes associated with tumor progression and poor outcomes. The ILC-unique FOXA1–ER axis led to retained ER chromatin binding after tamoxifen treatment, which facilitated tamoxifen resistance while remaining strongly dependent on ER signaling. Mechanistically, gained FOXA1 binding was associated with the autoinduction of FOXA1 in ILC through an ILC-unique FOXA1 binding site. Targeted silencing of this regulatory site resulted in the disruption of the feed-forward loop and growth inhibition in ILC. In summary, ILC is characterized by a unique chromatin state and FOXA1–ER axis that is associated with tumor progression, offering a novel mechanism of tamoxifen resistance. These results underscore the importance of conducting clinical trials dedicated to patients with ILC in order to optimize treatments in this breast cancer subtype.Significance:A unique FOXA1–ER axis in invasive lobular breast cancer promotes disease progression and tamoxifen resistance, highlighting a potential therapeutic avenue for clinical investigations dedicated to this disease.See related commentary by Blawski and Toska, p. 3668

Supplementary Data from A Distinct Chromatin State Drives Therapeutic Resistance in Invasive Lobular Breast Cancer

Summary Background Palbociclib added to endocrine therapy improves progression-free survival in hormone-receptor-positive, HER2-negative, metastatic breast cancer. The PALLAS trial aimed to investigate whether the addition of 2 years of palbociclib to adjuvant endocrine therapy improves invasive disease-free survival over endocrine therapy alone in patients with hormone-receptor-positive, HER2-negative, early-stage breast cancer. Methods PALLAS is an ongoing multicentre, open-label, randomised, phase 3 study that enrolled patients at 406 cancer centres in 21 countries worldwide with stage II–III histologically confirmed hormone-receptor-positive, HER2-negative breast cancer, within 12 months of initial diagnosis. Eligible patients were aged 18 years or older with an Eastern Cooperative Oncology Group performance score of 0 or 1. Patients were randomly assigned (1:1) in permuted blocks of random size (4 or 6), stratified by anatomic stage, previous chemotherapy, age, and geographical region, by use of central telephone-based and web-based interactive response technology, to receive either 2 years of palbociclib (125 mg orally once daily on days 1–21 of a 28-day cycle) with ongoing standard provider or patient-choice adjuvant endocrine therapy (tamoxifen or aromatase inhibitor, with or without concurrent luteinising hormone-releasing hormone agonist), or endocrine therapy alone, without masking. The primary endpoint of the study was invasive disease-free survival in the intention-to-treat population. Safety was assessed in all randomly assigned patients who started palbociclib or endocrine therapy. This report presents results from the second pre-planned interim analysis triggered on Jan 9, 2020, when 67% of the total number of expected invasive disease-free survival events had been observed. The trial is registered with ClinicalTrials.gov (NCT02513394) and EudraCT (2014-005181-30). Findings Between Sept 1, 2015, and Nov 30, 2018, 5760 patients were randomly assigned to receive palbociclib plus endocrine therapy (n=2883) or endocrine therapy alone (n=2877). At the time of the planned second interim analysis, at a median follow-up of 23·7 months (IQR 16·9–29·2), 170 of 2883 patients assigned to palbociclib plus endocrine therapy and 181 of 2877 assigned to endocrine therapy alone had invasive disease-free survival events. 3-year invasive disease-free survival was 88·2% (95% CI 85·2–90·6) for palbociclib plus endocrine therapy and 88·5% (85·8–90·7) for endocrine therapy alone (hazard ratio 0·93 [95% CI 0·76–1·15]; log-rank p=0·51). As the test statistic comparing invasive disease-free survival between groups crossed the prespecified futility boundary, the independent data monitoring committee recommended discontinuation of palbociclib in patients still receiving palbociclib and endocrine therapy. The most common grade 3–4 adverse events were neutropenia (1742 [61·3%] of 2840 patients on palbociclib and endocrine therapy vs 11 [0·3%] of 2903 on endocrine therapy alone), leucopenia (857 [30·2%] vs three [0·1%]), and fatigue (60 [2·1%] vs ten [0·3%]). Serious adverse events occurred in 351 (12·4%) of 2840 patients on palbociclib plus endocrine therapy versus 220 (7·6%) of 2903 patients on endocrine therapy alone. There were no treatment-related deaths. Interpretation At the planned second interim analysis, addition of 2 years of adjuvant palbociclib to adjuvant endocrine therapy did not improve invasive disease-free survival compared with adjuvant endocrine therapy alone. On the basis of these findings, this regimen cannot be recommended in the adjuvant setting. Long-term follow-up of the PALLAS population and correlative studies are ongoing. Funding Pfizer.

Adverse events (AE) during oncology clinical trials are typically reported using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), which provides information about the frequency and severity of AEs from the provider’s perspective. Instruments that track patient-reported outcomes (PRO) complement the CTCAE and provide additional patient-centered information about the toxicity profile of an anti-cancer drug. We conducted a single-arm, open-label phase II study of eribulin as first- or second-line therapy for metastatic hormone receptor-positive/HER2-negative (HR+/HER2−) or triple-negative breast cancer (TNBC). Patients were recruited simultaneously into each cohort by tumor subtype. The primary endpoint was overall response rate (ORR). Secondary endpoints included evaluation of toxicity by CTCAE and PRO instruments and agreement between CTCAE and PRO. The study also investigated single-nucleotide polymorphisms (SNPs) associated with treatment-induced neurotoxicity. 83 patients were enrolled: 45 into the HR+/HER2− cohort and 38 into the TNBC cohort. The ORR was 35.6% (90% CI 24–39%) in the HR+/HER2− cohort and 13.2% (90% CI 5–26%) in the TNBC cohort. Stable disease as the best response was recorded in 55.1% of patients with HR+/HER2− disease and 60.5% with TNBC. Toxicity analysis revealed a discordance between CTCAE and PRO assessment in many patients, with a focus on fatigue, alopecia, and neuropathy. Pharmacogenomic analysis identified SNPs associated with treatment-induced peripheral neuropathy. Eribulin is active in HER2− breast cancer. This study reveals that provider-assessed AEs can vary greatly from patient experiences. Future studies should incorporate CTCAE and PRO instruments to improve reporting of treatment-related AEs. ClinicalTrials.gov Registration: NCT01827787

PURPOSE The PALLAS study investigated whether the addition of palbociclib, an oral CDK4/6 inhibitor, to adjuvant endocrine therapy (ET) improves invasive disease-free survival (iDFS) in early hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2–) breast cancer. In this analysis, we evaluated palbociclib exposure and discontinuation in PALLAS. METHODS Patients with stage II-III HR+, HER2– disease were randomly assigned to 2 years of palbociclib with adjuvant ET versus ET alone. The primary objective was to compare iDFS between arms. Continuous monitoring of toxicity, dose modifications, and early discontinuation was performed. Association of baseline covariates with time to palbociclib reduction and discontinuation was analyzed with multivariable competing risk models. Landmark and inverse probability weighted per-protocol analyses were performed to assess the impact of drug persistence and exposure on iDFS. RESULTS Of the 5,743 patient analysis population (2,840 initiating palbociclib), 1,199 (42.2%) stopped palbociclib before 2 years, the majority (772, 27.2%) for adverse effects, most commonly neutropenia and fatigue. Discontinuation of ET did not differ between arms. Discontinuations for non–protocol-defined reasons were greater in the first 3 months of palbociclib, and in the first calendar year of accrual, and declined over time. No significant relationship was seen between longer palbociclib duration or ≥ 70% exposure intensity and improved iDFS. In the weighted per-protocol analysis, no improvement in iDFS was observed in patients receiving palbociclib versus not (hazard ratio 0.89; 95% CI, 0.72 to 1.11). CONCLUSION Despite observed rates of discontinuation in PALLAS, analyses suggest that the lack of significant iDFS difference between arms was not directly related to inadequate palbociclib exposure. However, the discontinuation rate illustrates the challenge of introducing novel adjuvant treatments, and the need for interventions to improve persistence with oral cancer therapies.

In the BrighTNess trial, carboplatin added to neoadjuvant chemotherapy (NAC) was associated with increased pathologic complete response (pCR) rates in patients with stage II/III triple-negative breast cancer (TNBC). In this matched cohort study, cases with a germline BRCA1/2 mutation (gBRCA; n = 75) were matched 1:2 with non-gBRCA controls (n = 150) by treatment arm, lymph node status, and age to evaluate pCR rates and association of benefit from platinum/PARP inhibitors with validated RNA expression-based immune, proliferation, and genomic instability scores among gBRCA with the addition of carboplatin ± veliparib to NAC. Among the well-matched cohorts, odds of pCR were not higher in gBRCA cancers who received standard NAC with carboplatin (OR 0.24, 95% CI [0.04-1.24], p = 0.09) or with carboplatin/veliparib (OR 0.44, 95% CI [0.10-1.84], p = 0.26) compared to non-gBRCA cancers. Higher PAM50 proliferation, GeparSixto immune, and CIN70 genomic instability scores were each associated with higher pCR rate in the overall cohort, but not specifically in gBRCA cases. In this study, gBRCA carriers did not have higher odds of pCR than non-gBRCA controls when carboplatin ± veliparib was added to NAC, and showed no significant differences in molecular, immune, chromosomal instability, or proliferation gene expression metrics.

Introduction The ability of breast magnetic resonance imaging (MRI) to predict pathologic complete response (pCR) to neoadjuvant systemic therapy (NST) varies across biological subtypes. We sought to determine how well breast MRI findings following initial treatment on the phase III BrighTNess trial correlated with pCR in patients with triple negative breast cancer (TNBC). Methods Baseline and mid-treatment imaging and pathologic response data were available in 519 patients with stage II-III TNBC who underwent NST as per protocol. MRI complete response (mCR) was defined as disappearance of all target lesion(s) and MRI partial response (mPR) as a ≥50% reduction in the largest tumor diameter. Results Overall, mCR was demonstrated in 116 patients (22%), whereas 166 (32%) had mPR and 237 (46%) had stable/progressive disease (SD/PD). The positive predictive value (PPV), negative predictive value, and overall accuracy of the mid-treatment MRI for pCR were 78%, 56%, and 61%, respectively; accuracy did not differ significantly between gBRCA mutation carriers and non-carriers (52% vs. 63%, p = 0.10). When compared to patients with SD/PD, those with mPR or mCR were 3.35-fold (95% CI 2.07–5.41) more likely to have pCR at surgery. MRI response during NST was significantly associated with eligibility for breast-conserving surgery following completion of treatment (93.1% for mCR vs. 81.6% for SD/PD, p Conclusions Complete response on mid-treatment MRI in the BrighTNess trial had a PPV of 78% for demonstration of pCR after completion of NST in TNBC. However, a substantial proportion of patients with mPR or SD/PD also achieved a pCR. Clinical trial registration NCT02032277 .

Importance In clinical practice, neoadjuvant endocrine therapy (NET) is rarely used despite being an effective treatment modality able to downstage tumors and facilitate breast-conserving surgery. Observations Using data from studies conducted since 2000, we provide readers with a critical in-depth review on clinical aspects related to the application of NET in the treatment of hormone receptor (HR)-positive/ERBB2 (formerly HER2)-negative breast cancer. This includes an overview of patient-selection criteria, regimen choice, treatment duration, evaluation of response by imaging, interpretation of pathology after treatment, and surgical considerations. Areas of controversy include the use of gene-expression tests for patient selection, treatment of premenopausal women, surgical management of the axilla after NET, and adjuvant systemic therapy decision-making, including the use of chemotherapy. Conclusions and relevance NET is an optimal treatment modality for a considerable proportion of postmenopausal women diagnosed with HR-positive tumors. The treatment landscape for HR-positive breast cancer is evolving, with novel agents and the growing use of gene expression profiling to define treatment selection. As such, it is likely that NET use will increase and the practical considerations outlined here will become more important.

IMPORTANCE: Adding carboplatin to standard neoadjuvant chemotherapy (NAC) in triple-negative breast cancer (TNBC) likely benefits a subset of patients; however, determinants of benefit are poorly understood. OBJECTIVE: To define the association of molecular subtype, tumor proliferation, and immunophenotype with benefit of carboplatin added to NAC for patients with stages II to III TNBC. DESIGN, SETTING, AND PARTICIPANTS: This was a prespecified secondary analysis of a phase 3, double-blind, randomized clinical trial (BrighTNess) that enrolled 634 women across 145 centers in 15 countries. Women with clinical stages II to III TNBC who had undergone pretreatment biopsy were eligible to participate. Whole transcriptome RNA sequencing was performed on the biopsy specimens. The prespecified end point was association of pathologic complete response (pCR) with gene expression–based molecular subtype, with secondary end points investigating established signatures (proliferation, immune) and exploratory analyses of immunophenotype. Data were collected from April 2014 to March 2016. The study analyses were performed from January 2018 to March 2019. INTERVENTIONS: Neoadjuvant chemotherapy with paclitaxel followed by doxorubicin and cyclophosphamide, or this same regimen with carboplatin or carboplatin plus veliparib. MAIN OUTCOMES AND MEASURES: Association of gene expression–based molecular subtype (PAM50 and TNBC subtypes) with pCR. RESULTS: Of the 634 women (median age, 51 [range, 22-78] years) enrolled in BrighTNess, 482 (76%) patients had evaluable RNA sequencing data, with similar baseline characteristics relative to the overall intention-to-treat population. Pathologic complete response was significantly more frequent in PAM50 basal-like vs nonbasal-like cancers overall (202 of 386 [52.3%] vs 34 of 96 [35.4%]; P = .003). Carboplatin benefit was not significantly different in basal-like vs nonbasal-like subgroups (P = .80 for interaction). In multivariable analysis, proliferation (hazard ratio, 0.36; 95% CI, 0.21-0.61; P

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6) were designed to induce cancer cell cycle arrest. Recent studies have suggested that these agents also exert other effects, influencing cancer cell immunogenicity, apoptotic responses, and differentiation. Using cell-based and mouse models of breast cancer together with clinical specimens, we show that CDK4/6 inhibitors induce remodeling of cancer cell chromatin characterized by widespread enhancer activation, and that this explains many of these effects. The newly activated enhancers include classical super-enhancers that drive luminal differentiation and apoptotic evasion, as well as a set of enhancers overlying endogenous retroviral elements that is enriched for proximity to interferon-driven genes. Mechanistically, CDK4/6 inhibition increases the level of several Activator Protein-1 (AP-1) transcription factor proteins, which are in turn implicated in the activity of many of the new enhancers. Our findings offer insights into CDK4/6 pathway biology and should inform the future development of CDK4/6 inhibitors.

Aim To present the pre-specified analyses of >5-years follow-up of the Phase III ALTTO trial. Patients and methods 8381 patients with stage I-III HER2 positive breast cancer randomised to chemotherapy plus 1-year of trastuzumab (T), oral lapatinib (L; no longer evaluated), trastuzumab followed by lapatinib (T→L), and lapatinib + trastuzumab (L+T). The primary endpoint was disease-free survival (DFS). A secondary analysis examined DFS treatment effects by hormone receptor status, nodal status and chemotherapy timing; time to recurrence; overall survival (OS) and safety (overall and cardiac). Results At a median follow-up of 6.9 years, 705 DFS events for L+T versus T were observed. Hazard Ratio (HR) for DFS was 0.86 (95% CI, 0.74–1.00) for L+T versus T and 0.93 (95% CI, 0.81–1.08) for T→L versus T. The 6-year DFS were 85%, 84%, and 82% for L+T, T→L, and T, respectively. HR for OS was 0.86 (95% CI, 0.70–1.06) for L+T versus T and 0.88 (95% CI, 0.71–1.08) for T→L versus T. The 6-year OS were 93%, 92%, and 91% for L+T, T→L, and T, respectively. Subset analyses showed a numerically better HR for DFS in favour of L+T versus T for the hormone-receptor-negative [HR 0.80 (95% CI, 0.64–1.00; 6-yr DFS% = 84% versus 80%)] and the sequential chemotherapy [HR 0.83 (95% CI, 0.69–1.00; 6-yr DFS% = 83% versus79%)] subgroups. Conclusion T+L did not significantly improve DFS and OS over T alone, both with chemotherapy, and, therefore, cannot be recommended for adjuvant treatment of early-stage HER2-positive breast cancer. Trial Registration clinicaltrials.gov Identifier NCT00490139 .

Adverse events (AE) during oncology clinical trials are typically reported using the National Cancer Institute Common Terminology Criteria for Adverse Events (CTCAE), which provides information about the frequency and severity of AEs from the provider's perspective. Instruments that track patient-reported outcomes (PRO) complement the CTCAE and provide additional patient-centered information about the toxicity profile of an anti-cancer drug.We conducted a single-arm, open-label phase II study of eribulin as first- or second-line therapy for metastatic hormone receptor-positive/HER2-negative (HR+/HER2-) or triple-negative breast cancer (TNBC). Patients were recruited simultaneously into each cohort by tumor subtype. The primary endpoint was overall response rate (ORR). Secondary endpoints included evaluation of toxicity by CTCAE and PRO instruments and agreement between CTCAE and PRO. The study also investigated single-nucleotide polymorphisms (SNPs) associated with treatment-induced neurotoxicity.83 patients were enrolled: 45 into the HR+/HER2- cohort and 38 into the TNBC cohort. The ORR was 35.6% (90% CI 24-39%) in the HR+/HER2- cohort and 13.2% (90% CI 5-26%) in the TNBC cohort. Stable disease as the best response was recorded in 55.1% of patients with HR+/HER2- disease and 60.5% with TNBC. Toxicity analysis revealed a discordance between CTCAE and PRO assessment in many patients, with a focus on fatigue, alopecia, and neuropathy. Pharmacogenomic analysis identified SNPs associated with treatment-induced peripheral neuropathy.Eribulin is active in HER2- breast cancer. This study reveals that provider-assessed AEs can vary greatly from patient experiences. Future studies should incorporate CTCAE and PRO instruments to improve reporting of treatment-related AEs. ClinicalTrials.gov Registration: NCT01827787.

Background Data on the efficacy of chemotherapy regimens in patients with advanced invasive lobular carcinoma (ILC) of the breast are limited. We investigated the efficacy of single-agent eribulin for the treatment of advanced ILC when compared with invasive ductal carcinoma (IDC). Patients and Methods Results from the eribulin arms of two phase III studies (305 [EMBRACE] and 301) and a single-arm, phase II study were pooled. The studies involved patients with metastatic breast cancer who had previously received treatment with an anthracycline and a taxane. In all three studies, the dose of eribulin mesylate was 1.4 mg/m2 given on days 1 and 8 of a 21-day cycle. Overall survival (OS), progression-free survival (PFS), and response rates in patients with ILC were assessed and compared with data from patients with IDC. Results In total, 1,152 patients were included in this analysis (118 patients with ILC and 1,034 patients with IDC). Median OS was similar in patients with ILC and IDC (13.4 vs. 13.5 months; hazard ratio [HR], 1.10; 95% confidence interval [CI], 0.87–1.38); as was median PFS (4.1 vs. 3.6 months; HR, 0.91; 95% CI, 0.72–1.14). There were no major differences in response rates between the two groups. Conclusion This retrospective analysis suggests that eribulin demonstrates similar efficacy in patients with ILC and IDC with metastatic disease who have previously received an anthracycline and a taxane.

Background: In HER2-positive breast cancer patients, timing from the end of (neo)adjuvant trastuzumab (T)-based therapy to diagnosis of metastatic breast cancer is the key factor in determining the optimal first-line treatment. There is currently lack of clear evidence to support the possible prognostic role of this interval and 12 months has been mostly empirically used. The present analysis aimed to investigate patterns of relapse, first-line choice and survival outcomes of patients with HER2-positive early breast cancer who relapsed after adjuvant T-based therapy depending on T-free interval (TFI, i.e. timing from end of adjuvant T to diagnosis of distant metastases). Methods: In ALTTO, HER2-positive early breast cancer patients were randomized to 1 year of either T alone, lapatinib (L) alone, their sequence (T–>L) or their combination (T+L). This exploratory analysis included only pts in the T or T+L arms who experienced a distant disease-free survival (DDFS) event. Two cohorts of patients were defined depending on TFI: group A (TFI of 12 months). Baseline characteristics, patterns of relapse, first-line choice and overall survival (OS) were compared. OS was defined as time between date of DDFS event to death; age at diagnosis, tumor size and hormone receptor status were the variables included in the final multivariate models. Results: Out of 8,381 patients included in ALTTO, 404 patients in the T and T+L arms developed a DDFS event, of whom 201 occurred 12 months (group B) after the end of adjuvant T. Patients in group A were older (p=0.013), had larger tumors (p=0.004) and more frequently hormone receptor-negative disease (p Conclusions: In the ALTTO trial, HER2-positive early breast cancer patients who experienced shorter TFI (i.e. 12 months) following adjuvant T-based therapy had inferior OS after the diagnosis of distant recurrence. Given its prognostic value, TFI can help to individualize clinical recommendations and to design future trials in the metastatic setting for patients relapsing after prior exposure to anti-HER2 therapy for early disease. Citation Format: Matteo Lambertini, Dominique Agbor-Tarh, Otto Metzger-Filho, Noam Ponde, Francesca Poggio, Florentine Hilbers, Larissa A Korde, Saranya Chumsri, Olena Werner, Lucia Del Mastro, Rafael Caparica, Volker Moebus, Alvaro Moreno-Aspitia, Martine Piccart, Evandro de Azambuja. Prognostic role of distant disease-free interval from completion of adjuvant trastuzumab in HER2-positive early breast cancer: Analysis from the ALTTO (BIG 2-06) trial [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 PD3-04.

Cyclin-dependent kinases 4 and 6 (CDK4/6) are fundamental drivers of the cell cycle and are required for the initiation and progression of various malignancies. Pharmacological inhibitors of CDK4/6 have shown significant activity against several solid tumours. Their primary mechanism of action is thought to be the inhibition of phosphorylation of the retinoblastoma tumour suppressor, inducing G1 cell cycle arrest in tumour cells. Here we use mouse models of breast carcinoma and other solid tumours to show that selective CDK4/6 inhibitors not only induce tumour cell cycle arrest, but also promote anti-tumour immunity. We confirm this phenomenon through transcriptomic analysis of serial biopsies from a clinical trial of CDK4/6 inhibitor treatment for breast cancer. The enhanced anti-tumour immune response has two underpinnings. First, CDK4/6 inhibitors activate tumour cell expression of endogenous retroviral elements, thus increasing intracellular levels of double-stranded RNA. This in turn stimulates production of type III interferons and hence enhances tumour antigen presentation. Second, CDK4/6 inhibitors markedly suppress the proliferation of regulatory T cells. Mechanistically, the effects of CDK4/6 inhibitors both on tumour cells and on regulatory T cells are associated with reduced activity of the E2F target, DNA methyltransferase 1. Ultimately, these events promote cytotoxic T-cell-mediated clearance of tumour cells, which is further enhanced by the addition of immune checkpoint blockade. Our findings indicate that CDK4/6 inhibitors increase tumour immunogenicity and provide a rationale for new combination regimens comprising CDK4/6 inhibitors and immunotherapies as anti-cancer treatment.

Background In HER2-positive breast cancer, time elapsed between completion of (neo)adjuvant trastuzumab and diagnosis of metastatic disease (a € trastuzumab-free interval', TFI) is crucial to choose the optimal first-line treatment. Nevertheless, there is no clear evidence to support its possible prognostic role. Methods In the Adjuvant Lapatinib and/or Trastuzumab Treatment Optimisation (ALTTO) trial, patients with HER2-positive early breast cancer were randomised to 1 year of either trastuzumab alone, lapatinib alone, their sequence or their combination. This exploratory analysis included only patients in the trastuzumab alone or trastuzumab plus lapatinib arms who developed a distant disease-free survival (DDFS) event. Overall survival (OS) was defined as time between date of DDFS event and death; age at diagnosis, tumour size and hormone receptor status were the variables included in the multivariate models. Results Out of 8381 patients included in ALTTO, 404 patients in the trastuzumab alone and trastuzumab plus lapatinib arms developed a DDFS event, of which 201 occurred 12 months (group B) after completion of adjuvant trastuzumab. No significant difference in location of first DDFS event was observed (p=0.073); a numerically higher number of patients in group A than in group B developed brain metastasis (26% vs 15%). Choice of first-line therapy differed between the two groups (p=0.022): in group A, more patients received lapatinib (25% vs 11%) and less pertuzumab (8% vs 17%). Median OS was 29.3 and 18.4 months in groups B and A, respectively (adjusted HR 0.69; 95% CI 0.54-0.89; p=0.004). The longer OS for patients in group B was observed across the analysed subgroups without interaction according to hormone receptor status (p=0.814) nor type of administered adjuvant anti-HER2 treatment (p=0.233). Conclusions TFI has prognostic value in patients with HER2-positive early breast cancer treated with adjuvant trastuzumab-based therapy. TFI is a valid tool to better individualise clinical recommendations and to design future first-line treatment trials for metastatic patients., SCOPUS: ar.j, info:eu-repo/semantics/published

10597 Background: Identification of a germline mutation in a breast cancer predisposition gene has implications for the patients and their families. The National Comprehensive Cancer Network (NCCN) has published guidelines for genetic testing. In Brazil, this assessment is covered by health insurance in accordance with criteria defined by the National Supplementary Health Agency (ANS). For the majority of the population, served by the public health system (SUS), the assessment is not routinely available. Methods: In order to determine the prevalence rates of NCCN and ANS criteria for germline testing in breast cancer (primary outcome) we retrospectively analyzed data from patients treated at two SUS oncology centers in Belo Horizonte, Minas Gerais, Brazil, between 01/01/18 and 12/31/19. The secondary outcomes were comparisons between the groups with and without germline testing criteria (NCCN and ANS) regarding overall survival, clinical and epidemiological characteristics. The association between qualitative variables was calculated using the Chi-square and Fisher tests. The Kaplan-Meier method was used to analyse the survival data and the differences between the groups were tested using the log-rank test. The level of significance was 5%. Results: A total of 357 patients were included in the final analysis. The presence of germline testing criteria were found in 126 patients (35%) according to NCCN guidelines and in 82 patients (23%) according to ANS guidelines. None of them were tested for germline mutations. The most common criteria were women up to 60 years old with triple negative tumors (n = 43, 12% of all patients) and diagnosis of cancer up to 45 years old (n = 75, 21% of all patients) according to ANS and NCCN criteria, respectively. When the group of patients who met at least one criterion for germline testing were compared with the group who did not met any criteria, we found in the first group: more ductal carcinomas and less lobular tumors (p = 0.009), more grade 3 tumors (p = 0.002), more triple negative tumors (p < 0.001), more neoadjuvant treatments (p = 0.008) and less hormonal therapies (p = 0.011). After a median follow up of 13.5 months there were 22 deaths in the cohort, 7 in the group with testing criteria (5.7%) and 15 in the group without testing criteria (6.4%). There was no statistical significant difference between the groups in terms of overall survival (p = 0.77). Conclusions: To our knowledge this is the first study to evaluate the prevalence of NCCN and ANS criteria for germline testing in patients with breast cancer treated in the Brazilian public health system. Our results show that more than a third of those patients are candidates for germline testing. Moreover, the data highlight a serious shortcoming in the management of breast cancer and must be considered in the development of public health policies for routine germline testing in that population.

Introduction The necessity of using granulocyte-colony stimulating factor (G-CSF) during dose-dense (DD) paclitaxel (T) after doxorubicin and cyclophosphamide (AC) is unclear. Methods This was a retrospective cohort study including patients with stage I-III breast cancer treated at Dana-Farber Cancer Institute with adjuvant DD-ACT between January 2011 and December 2013. Descriptive analyses evaluating patterns of G-CSF utilization during T were performed. Results Overall, 156 patients were treated with DD-ACT by 26 providers. The majority of patients (135, 87%) received at least one dose of G-CSF during T (group 1), 17% of these patients received it in only one cycle and 48% received it in all four cycles. Reasons for omitting G-CSF included high baseline absolute neutrophil count and pain. Twenty-one (13%) patients did not receive any G-CSF during T (group 2). Respectively, 94% and 90% of patients completed the treatment in groups 1 and 2. There were no cases of treatment cessation due to neutropenia. Six percent of patients in group 1 had at least one treatment delay. There were no treatment delays reported in group 2. Variation in the use of G-CSF by provider and by patient was found, with 11 providers choosing not to use G-CSF in at least one patient. Conclusions We identified substantial variation in the use of G-CSF within the practice. However, omission of G-CSF was not associated with treatment delays or adverse events. Prospective studies are warranted to formally test whether routine G-CSF is necessary during dose-dense T therapy.

Few contemporary data are available that compare incidence and survival of metastatic breast cancer between ductal and lobular carcinomas. Using the Surveillance, Epidemiology, and End Results-9 registries, we identified 10,639 patients with de novo metastatic breast cancer diagnosed from 1990 to 2011. Annual age-adjusted incidence rates and annual percent changes (APCs) were analyzed. Multivariable Cox regression models were used to investigate the impact of year of diagnosis and histology on overall survival. 9250 (86.9 %) patients had ductal and 1389 (13.1 %) had lobular carcinomas. Metastatic breast cancer incidence increased slightly over time for ductal (APC = +1.7, 95 % confidence interval (CI) = +1.0 to +2.4) and lobular carcinomas (APC = +3.0, 95 % CI = +1.8 to +4.3). Median overall survival was 22 months among the whole cohort. More recent year of diagnosis was associated with better overall survival only for patients with ductal carcinomas (interaction p value = 0.006), with an adjusted hazard ratio of death for every five-year increment in the date of diagnosis of 0.93 (95 % CI = 0.91-0.95) among ductal carcinomas, compared with 1.05 (95 % CI = 0.95-1.10) among lobular carcinomas. Overall survival was longer for lobular versus ductal carcinomas (28 versus 21 months, respectively; adjusted hazard ratio of death = 0.93, 95 % CI = 0.87-0.99), but the magnitude of this effect was attenuated among the cohort restricted to hormone receptor-positive tumors. In this population-based analysis, incidence rates of metastatic breast cancer at presentation increased slightly over time for both histologies, and particularly for lobular tumors. A modest improvement in metastatic breast cancer median overall survival was observed, but was apparently limited to ductal carcinomas.

Background: Survival for metastatic breast cancer (MBC) patients (pts) has modestly improved over time. Until the early 2000's, incidence rates for invasive lobular carcinoma (ILC) had steadily risen, in contrast to the stable rates observed for invasive ductal carcinoma (IDC). Historically, ILC was deemed to have a more favorable prognosis than IDC. Nevertheless, data on recent time trends in incidence and survival of lobular vs. ductal histology among newly diagnosed MBC pts are limited. Pts and Methods: Using the Surveillance, Epidemiology, and End Results (SEER) 9 registries, we included 10,767 pts diagnosed with de novo lobular or ductal MBC from 1990-2011, and followed through 2012. Time trends in annual age-adjusted incidence rates were analyzed, stratified by histology. Multivariable Cox regression models were fit to investigate the association of year of diagnosis and overall survival (OS) by stratum, adjusting for features presented in Table 1. We examined interactions between year of diagnosis and histology. In sensitivity analyses, we modeled year of diagnosis as categorical, and restricted the cohort to hormone-receptor positive pts. Table 1IDC N= 9,376 (87%)ILC N= 1,391 (13%)Cohort characteristics%Age, yearsƚ Results: 9,376 (87%) pts had IDC and 1,391 (13%) had ILC. Overall, we found a 1.4 fold increase in incidence rates for de novo MBC over the study period, (with a 1.3- and 2.6-fold increase for IDC and ILC, respectively). OS improved over the study period for the overall cohort (Hazard ratio (HR) of death=0.99; 95% confidence interval (CI)=0.98-0.99; 1% decrease/year; 5% decrease/5 years; p=.0059 for the interaction year of diagnosis-histology on OS). ILC pts had better outcomes than IDC pts (median OS=28 vs. 21 months; adjusted HR of death= 0.93; 95%CI=0.87-0.99). For IDC pts, we found a statistically significant improvement in OS over time (HR of death=0.98; 95%CI=0.98-0.99; 2% decrease/year; 6% decrease/5 years). However, we observed no significant change in survival outcomes for ILC pts (HR of death=1.01; 95%CI=0.99-1.02) (Table 1). Results from sensitivity analyses were similar. Conclusions: From 1990-2011, incidence rates for de novo MBC increased. In this cohort, ILC pts had a better prognosis than IDC pts. Nevertheless, although we found an expected overall improvement in OS for MBC pts, this effect was restricted to IDC pts, with no significant improvement among ILC pts. Dedicated studies are warranted to understand whether our results can be confirmed in other datasets and to investigate the reasons driving this discrepancy, such as the impact of patterns of care, new drug approvals, and tumor molecular subtype. Citation Format: Di Meglio A, Freedman RA, Lin NU, Barry WT, Metzger-Filho O, Keating NL, Winer EP, Vaz-Luis I. Time trends in incidence rates and survival for women with de novo metastatic lobular vs. ductal carcinoma, a population-based study. [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 P1-07-08.

This retrospective analysis conducted using data from patients enrolled onto the Herceptin Adjuvant has two objectives: The first is to evaluate the impact of the time interval between the end of adjuvant trastuzumab and distant recurrence (TDRI) upon overall survival (OS). The second is to describe the duration of trastuzumab-based regimens in the metastatic setting for patients previously treated with adjuvant trastuzumab. The first objective included 187 patients treated with adjuvant trastuzumab and diagnosed with distant recurrence at 4-year median follow-up. The second objective included data from questionnaires sent to investigators retreating patients with trastuzumab upon distant recurrence: 144 of 156 questionnaires were returned (93 %), and 90 patients were selected based on available clinical information and consent for subsequent studies. There was no statistically significant relationship between TDRI following 1 year of adjuvant trastuzumab and OS from distant recurrence: hazard ratio 0.991, p = 0.46. The median OS from distant recurrence was numerically longer among patients with a TDRI of ≥12 months (n = 103) than

// Sandeep K. Singhal 1, * , Nawaid Usmani 1, * , Stefan Michiels 2, 3 , Otto Metzger-Filho 4 , Kamal S. Saini 5 , Olga Kovalchuk 6, 7, * , Matthew Parliament 1, * 1 Department of Oncology, Cross Cancer Institute, University of Alberta, Edmonton, Canada 2 Service de Biostatistique et d’Epidemiologie, Gustave Roussy, Villejuif, France 3 INSERM U1018, CESP, Universite Paris-Sud, Villejuif, France 4 Department of Medical Oncology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA, USA 5 Quantum Health Analytics SPRL, Liege, Belgium 6 Department of Biological Sciences, University of Lethbridge, Lethbridge, Canada 7 Canada Cancer and Aging Research Laboratories Ltd., Lethbridge, Canada * These authors contributed equally to the work Correspondence to: Matthew Parliament, e-mail: matthew.parliament@albertahealthservices.ca Olga Kovalchuk, e-mail: olga.kovalchuk@uleth.ca and olga.kovalchuk@ccarl.ca Keywords: DNA methylation, breast cancer, epigenetics, expression, microarray Received: August 11, 2015 Accepted: November 16, 2015 Published: December 08, 2015 ABSTRACT Until recently, an elevated disease risk has been ascribed to a genetic predisposition, however, exciting progress over the past years has discovered alternate elements of inheritance that involve epigenetic regulation. Epigenetic changes are heritably stable alterations that include DNA methylation, histone modifications and RNA-mediated silencing. Aberrant DNA methylation is a common molecular basis for a number of important human diseases, including breast cancer. Changes in DNA methylation profoundly affect global gene expression patterns. What is emerging is a more dynamic and complex association between DNA methylation and gene expression than previously believed. Although many tools have already been developed for analyzing genome-wide gene expression data, tools for analyzing genome-wide DNA methylation have not yet reached the same level of refinement. Here we provide an in-depth analysis of DNA methylation in parallel with gene expression data characteristics and describe the particularities of low-level and high-level analyses of DNA methylation data. Low-level analysis refers to pre-processing of methylation data (i.e. normalization, transformation and filtering ), whereas high-level analysis is focused on illustrating the application of the widely used class comparison , class prediction and class discovery methods to DNA methylation data. Furthermore, we investigate the influence of DNA methylation on gene expression by measuring the correlation between the degree of CpG methylation and the level of expression and to explore the pattern of methylation as a function of the promoter region.

Purpose To evaluate the relative effectiveness of letrozole compared with tamoxifen for patients with invasive ductal or lobular carcinoma. Patients and Methods Patients diagnosed with early-stage invasive ductal carcinoma (IDC) or classic invasive lobular carcinoma (ILC) who were randomly assigned onto the Breast International Group (BIG) 1-98 trial and who had centrally reviewed pathology data were included (N = 2,923). HER2-negative IDC and ILC were additionally classified as hormone receptor–positive with high (luminal B [LB] –like) or low (luminal A [LA] –like) proliferative activity by Ki-67 labeling index. Survival analyses were performed with weighted Cox models that used inverse probability of censoring weighted modeling. Results The median follow-up time was 8.1 years. In multivariable models for disease-free survival (DFS), significant interactions between treatment and histology (ILC or IDC; P = .006) and treatment and subgroup (LB like or LA like; P = .01) were observed. In the ILC subset, there was a 66% reduction in the hazard of a DFS event with letrozole for LB (hazard ratio [HR], 0.34; 95% CI, 0.21 to 0.55) and a 50% reduction for LA subtypes (HR, 0.50; 95% CI, 0.32 to 0.78). In the IDC subset, there was a significant 35% reduction in the hazard of a DFS event with letrozole for the LB subtype (HR, 0.65; 95% CI, 0.53 to 0.79), but no difference between treatments was noted for IDC and the LA subtype (HR, 0.95; 95% CI, 0.76 to 1.20). Conclusion The magnitude of benefit of adjuvant letrozole is greater for patients diagnosed with lobular carcinoma versus ductal carcinoma.

Background: Recent consensus guideline on margins for breast conserving surgery recommends the use of no ink on tumor as the standard for an adequate margin. Current recommendation extends to invasive lobular carcinoma (ILC), however the data in this subset is limited by small numbers. In the present analysis we sought to evaluate the influence of margin status on outcomes in ILC and mixed tumors. Methods: We performed retrospective cohort study and reviewed 809 eligible patients diagnosed with ILC (337 with pure ILC; 472 with mixed ILC) with Stage I –III treated at Dana Farber/Brigham and Women’s Cancer Center (DFBWCC) between May 1997 and Dec 2007. Clinico-pathologic data was extracted following the Clinical Research Information Systems (CRIS) Database procedures and manually reviewed to confirm inclusion and details of margin status. Margin status was defined using the last ASCO/ASTRO/SSA consensus guidelines criteria. Analysis results were considered to be statistically significant when the two-tailed p-value was Results: Breast conservation was performed in 399 patients (49%). Margin status at the initial attempt for breast conservation was defined as follows: 180 (45%) negative, 64 (16%) positive, 71 (18%) ≤ 1mm margin, and 84 (21%) close margins (> 1 and < 3 mm). Following initial lumpectomy, 102 (25%) patients underwent additional surgery (96 re-excisions and 6 mastectomies) and residual invasive disease was found in 40 patients. Whole-breast radiation therapy was performed in 376 patients (96%). In multivariate models adjusted for classic clinico-pathologic factors, tumor size (HR= 1.8 95% CI 1.0 to 3.3, p=0.05), multifocality (HR= 2.0 95% CI 1.1 to 3.6, p= 0.02) and ILC subtype (HR= 2.0 95% CI 1.0 to 3.7, p=0.04) were correlated with positive margins, while year of diagnosis, age and pre-surgical MRI findings were not statistically significant. With 72 months median follow-up, 12 ipsilateral breast cancers (3.1%), 5 other locoregional (1.2%) and 15 distant (3.8%) recurrences were observed after definitive breast conserving therapy. The incidence of locoregional recurrence (LRR) was 4.3% and similar for ILC and mixed ILC (p=0.76). In univariate analysis positive surgical margin was associated with LRR (HR=5.1, p= 0.03) and disease-free survival (DFS) (HR=8.9, p≤ .001), but due to limited number of cases and events this could not be adjusted for other clinico-pathologic prognostic factors in a mulitvariate model. Close surgical margins, margins within 1mm and multifocality were not associated with increased LRR or worse DFS. Re-excision did not impact on DFS for patients with close margin (p= 0.57) and within 1 mm margin (p= 0.85). By contrast, significant improvement of DFS following re-excision was observed in patients with positive margin (p= 0.01). Conclusions: Following lumpectomy, local recurrence rates for ILC patients with close surgical margin and ≤ 1mm margin are low and equivalent to those in patients with negative margins. This study supports the validity of using no ink on tumor as the standard for an adequate margin for patients diagnosed with pure or mixed ILC treated with multimodality therapy. Citation Format: Yasuaki Sagara, William T Barry, Ines Vaz-Luis, Fatih Aydogan, Jane E Brock, Eric P Winer, Mehra Golshan, Otto Metzger-Filho. Effect of margin width on local recurrence in invasive lobular carcinoma treated with multimodality therapy [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-16-01.

Background: Invasive lobular carcinoma (ILC) represents the second most common breast cancer (BC) subtype and is usually characterized as hormone-receptor positive, low-to-intermediate histologic grade, and human epidermal growth factor receptor (HER) 2-negative. In the early-stage setting, ILCs are associated with lower rates of pathological response to preoperative chemotherapy compared with invasive ductal carcinoma (IDC). This exploratory analysis investigated the magnitude of benefit of single-agent eribulin for the treatment of advanced ILC using data from three clinical trials in women with advanced BC. We also describe the patterns of response and survival outcomes compared with IDC. Methods: Individual patient (pt) data from the experimental arms of two phase III studies (305 and 301) and a single-arm, phase II study were pooled for the present analysis. Study 305 (EMBRACE) randomized pts treated with ≥2 lines of chemotherapy for advanced BC to receive eribulin or treatment of physician's choice. In study 301, pts treated with ≤2 lines of chemotherapy for advanced BC were randomized to receive eribulin or capecitabine. In the phase II study, pts who had received ≥3 lines of chemotherapy were treated with eribulin. Overall survival (OS) and progression-free survival (PFS) analyses were adjusted by study, estrogen receptor (ER) and HER2 status, and number of lines of therapy for advanced disease. Results: The three studies included 1353 eribulin-treated pts. Of the 1152 pts included in the present analysis, 118 were classified as ILC and 1034 as IDC. Median age of ILC and IDC pts was 58 years and 55 years, respectively. ER and/or progesterone receptor (PgR) positivity was more common in ILC (ER = 69%, PgR = 55%) than IDC (ER = 60%, PgR = 48%), while HER2 positivity was less frequent in ILC than IDC (9% vs 16%). A total of 52.5% of ILC and 61.4% of IDC pts received ≥3 lines of chemotherapy (for any stage BC) prior to eribulin. Pts with ILC and IDC had similar median OS (13.4 vs 13.5 months; hazard ratio [HR] = 1.10; 95% confidence intervals [CIs] 0.87, 1.38) and PFS (4.1 vs 3.6 months; HR = 0.91; 95% CIs 0.72, 1.14). Investigator-evaluated tumor response rates are shown in the table. Table: Best overall tumor responses (by investigator review)Response, %Invasive lobular carcinoma, n = 110Invasive ductal carcinoma, n = 985Objective response rate: CR + PR (95% CIs)15.5 (9.3, 23.6)14.8 (12.7, 17.2)Complete response (CR)00.4Partial response (PR)15.514.4Stable disease (SD)53.652.7Progressive disease (PD)26.428.9Clinical benefit rate: CR + PR + SD ≥6 months (95% CIs)29.1 (20.8, 38.5)28.6 (25.8, 31.6)Not evaluable4.53.6 Conclusions: In this exploratory, pooled analysis, magnitude of benefit from single-agent eribulin did not differ between the ILC and IDC cohorts. While there was a limited numbers of pts with ILC, response rates, PFS, and OS were similar for the two pt groups. The results with eribulin for advanced ILC contrast with data for other agents in early-stage settings, where ILC is generally less responsive to chemotherapy than IDC. These findings may, however, underline changes in the disease biology after exposure to previous therapies or changes inherent to disease progression. Citation Format: Javier Cortés, José Pérez, Yi He, Otto Metzger-Filho. Efficacy of eribulin in patients with invasive lobular carcinoma of the breast: data from a pooled analysis [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-13-06.

Recent consensus guidelines on margins for breast-conserving surgery (BCS) recommend the use of “no ink on tumor” as the standard for an adequate margin. The recommendations extend to invasive lobular carcinoma (ILC), but the data on this subset are limited. We reviewed our modern dataset on margin status with outcomes of ILC. We performed a retrospective cohort study on 736 patients with a diagnosis of stage I–III ILC treated at our cancer center between May 1997 and December 2007. Clinicopathologic data were extracted from the Clinical Research Information Systems Database. Margin status was defined using the latest ASCO/ASTRO/SSO consensus guideline criteria. The initial surgery performed was mastectomy in 352 patients (48 %) and BCS in 384 patients (52 %). In multivariate analysis, tumor size and multifocality were significantly associated with high rates of mastectomy and positive surgical margins at initial BCS. After initial BCS, additional surgery was performed in 92 patients (24 %). During a 72-month median follow-up period, 12 (3.1 %) ipsilateral breast tumor recurrences (IBTR) and 5 (1.3 %) other locoregional recurrences (LRR) were observed. Patients with margins with ink on tumor who did not receive further surgery were found to have significantly increased LRR [odds ratio (OR) 5.5; p = 0.02] and IBTR (OR 8.5; p = 0.006), whereas patients with close margins (1–3 mm) and margins within 1 mm were not. Our study supports the validity of using “no ink on tumor” as the standard for a negative margin for pure and mixed ILC treated with multimodality therapy.

Background Although several randomised trials in patients with triple-negative breast cancer have shown that the addition of carboplatin, with or without poly(ADP-ribose) polymerase (PARP) inhibitors, to neoadjuvant chemotherapy increases the likelihood of achieving a pathological complete response, the use of these therapies in this setting has remained controversial. The BrighTNess trial was designed to assess the addition of the PARP inhibitor veliparib plus carboplatin or carboplatin alone to standard neoadjuvant chemotherapy in triple-negative breast cancer. Methods We did a phase 3, randomised, double-blind, placebo-controlled trial (BrighTNess) across 145 sites in 15 countries. Patients aged 18 years and older with previously untreated histologically or cytologically confirmed clinical stage II-III triple-negative breast cancer, who were candidates for potentially curative surgery and had an Eastern Cooperative Oncology Group performance status of 0 or 1, were randomly assigned (2:1:1) by an interactive response technology system via permuted blocks (block size of four) within strata to receive one of three segment 1 regimens: paclitaxel (80 mg/m(2) intravenously weekly for 12 doses) plus carboplatin (area under the curve 6 mg/mL per min, intravenously every 3 weeks, for four cycles) plus veliparib (50 mg orally, twice a day); paclitaxel plus carboplatin plus veliparib placebo (twice a day); or paclitaxel plus carboplatin placebo (every 3 weeks for four cycles) plus veliparib placebo. Following segment 1, all patients were assigned to segment 2 in which they received doxorubicin and cyclophosphamide every 2-3 weeks for four cycles. Randomisation for segment 1 was stratified by germline BRCA mutation status, nodal stage, and planned schedule of doxorubicin and cyclophosphamide administration. The primary endpoint was pathological complete response in breast and lymph nodes as determined by site pathologists following completion of neoadjuvant therapy. Efficacy analyses were done by intention to treat and safety analyses included all patients who received at least one dose of study treatment. These are the first results of an ongoing clinical trial; the data cutoff for the analyses presented was Dec 8, 2016. This study is registered with ClinicalTrials.gov, number NCT02032277. Findings Between April 4, 2014, and March 18, 2016, 634 patients were randomly assigned: 316 to paclitaxel plus carboplatin plus veliparib, 160 to paclitaxel plus carboplatin, and 158 to paclitaxel alone. The proportion of patients who achieved a pathological complete response was higher in the paclitaxel, carboplatin, and veliparib group than in patients receiving paclitaxel alone (168 [53%] of 316 patients vs 49 [31%] of 158, p

Since 2005, aromatase inhibitors (AIs) have been the adjuvant treatment of choice for postmenopausal women with early breast cancer (BC). In this study we characterize the adoption of AIs in Portugal, variables associated with treatment administration, and compare its effectiveness (either in monotherapy or sequential therapy) to tamoxifen monotherapy (TAM).This was a retrospective cohort study that included postmenopausal women with stage I-III hormone receptor (HR) positive BC diagnosed from 2006 to 2008 and treated with adjuvant endocrine therapy in four participating institutions.Of the 1283 eligible patients, 527 (41%) received an AI (16% as monotherapy, 25% as sequential therapy) and 756 (59%) TAM. Patients treated with AI had less differentiated tumors, with higher TNM stage, and were more frequently HER2-positive. Use of AI also differed by center (use range from 33% to 75%, p 0.001). With a median follow-up of 6.3 years and controlling for clinicopathological and treatment characteristics, treatment with AI had a better overall survival (OS) when compared with TAM (adjusted-HR 0.55, 95% CI 0.37-0.81).AIs were successfully introduced as adjuvant treatment for HR-positive BC in Portuguese hospitals. Its use was influenced by tumor and patient characteristics, but also center of care. In this large cohort, AI use was associated with an OS benefit.

Purpose To document the rate and outcome of trastuzumab-associated cardiac dysfunction in patients following 1 or 2 years of adjuvant therapy. Patients and Methods The Herceptin Adjuvant (HERA) trial is a three-arm, randomized trial comparing 2 years or 1 year of trastuzumab with observation in 5,102 patients with human epidermal growth factor receptor 2 (HER2) –positive early-stage breast cancer. Cardiac function was closely monitored. Eligible patients had left ventricular ejection fraction (LVEF) ≥ 55% at study entry following neoadjuvant chemotherapy with or without radiotherapy. This 8-year median follow-up analysis considered patients randomly assigned to 2 years or 1 year of trastuzumab or observation. Results The as-treated safety population for 2 years of trastuzumab (n = 1,673), 1 year of trastuzumab (n = 1,682), and observation (n = 1,744) is reported. Cardiac adverse events leading to discontinuation of trastuzumab occurred in 9.4% of patients in the 2-year arm and 5.2% of patients in the 1-year arm. Cardiac death, severe congestive heart failure (CHF), and confirmed significant LVEF decrease remained low in all three arms. The incidence of severe CHF (0.8%, 0.8%, and 0.0%, respectively) and confirmed significant LVEF decrease (7.2%, 4.1%, and 0.9%, respectively) was significantly higher in the 2-year and 1-year trastuzumab arms compared with the observation arm. Severe CHF was the same for 2-year and 1-year trastuzumab. Of patients with confirmed LVEF decrease receiving 2-year trastuzumab, 87.5% reached acute recovery. Of patients with confirmed LVEF decrease receiving 1-year trastuzumab, 81.2% reached acute recovery. Conclusion Long-term assessment at 8-year median follow-up confirms the low incidence of cardiac events for trastuzumab given sequentially after chemotherapy and radiotherapy, and cardiac events were reversible in the vast majority of patients.

510 Background: In TNBC, the interplay between immunophenotype, tumor proliferation (prolif) and achievement of pathologic complete response (pCR) with neoadjuvant chemotherapy (NAC) remains unknown. Methods: RNA seq was performed on pre-tx research biopsies of stage II/III TNBC enrolled in BrighTNess. NAC regimens included paclitaxel alone or with carboplatin (Cb) or Cb plus veliparib, followed by AC. Computational analysis included subtyping (i.e. PAM50, Pietenpol), prolif (PAM50) and GeparSixto immune signature (GSIS). Cb-containing arms were combined due to similar pCR. Results: High quality RNA seq data was obtained from 482 of 634 pts. PAM50 classified 80.1% of tumors as basal-like. TNBC subtypes were mostly BL1 or BL2 (23.3%), IM (22.4%) or M/MSL (31.7%); 6% were LAR. pCR was higher for basal vs non-basal tumors (52.3% vs 35.4%, p = 0.003). IM had the highest pCR rate (64.2%, 95% CI 59.9%,68.5%). Basal-like was not a significant predictor for Cb benefit (p-interaction = 0.8). Prolif (OR = 0.30 p < 0.001) and GSIS (OR 0.68 p < 0.001) were significantly correlated with pCR but did not correlate with each other (Pearson’s r2 = 0.027). In multivariate analysis, prolif (HR = 0.36 95% CI, 0.21-0.61 p = 0.0002) and GSIS (HR = 0.62 95% CI, 0.49-0.79 p < 0.0001) increased the ability to predict pCR beyond standard clinico-pathologic variables (likelihood ratio = 14.9, p = 0.0001115). Among all pts, those above the median for both prolif. and GSIS had the highest pCR (67%; 84/125) while those below the median for both had the lowest pCR rate (34%; 42/125). Tumors with higher inferred CD8+ T-cell infiltration demonstrated greater benefit from Cb using either TIMER (HR = 0.83 [0.73-0.95]) or CIBERSORT (HR = 0.83 [0.76-0.91]). Tumors with higher inferred total macrophages, particularly immune suppressive M2 macrophages had a higher pCR rate on the non-Cb arm (AC-T) using CIBERSORT (HR = 1.27 [1.07,1.50]). Conclusions: Immunophenotype and proliferation are independent predictors of pCR to standard NAC regimens in TNBC. PAM50 is not a significant predictor of Cb benefit. Exploratory findings suggest that tumor infiltrating immunophenotype (i.e. CD8 T cells and macrophages) may predict response to specific NAC regimens in TNBC. Clinical trial information: NCT02032277.

502 Background: HER2 targeted therapy without chemotherapy may be insufficient to completely eradicate a HER2+ cancer in cases of significant intratumor HER2 heterogeneity (ITH-HER2). Methods: We conducted a single-arm phase II study enrolling centrally confirmed HER2+ breast cancer. Pts received 6 cycles of T-DM1 plus Pertuzumab before surgery. Central ITH-HER2 was assessed on baseline ultrasound-guided core biopsies from 2 distinct areas of each tumor (3 cores/site). ITH-HER2 was defined as at least one of the six areas demonstrating either 1) HER2 positivity by FISH in > 5% and < 50% of tumor cells (i.e., CAP guideline) or 2) an area of tumor that tested HER2 negative. The primary objective is the association between pathologic complete response (pCR) and ITH, stratified by ER status. pCR defined as residual cancer burden (RCB) 0. Results: 164 pts with centrally confirmed HER2+ tumors were enrolled from 1/2015 to 1/2018. 2 pts withdrew consent. Median tumor size by imaging was 2.8 cm (IQR 2.1-3.8cm); 111 (69%) were ER+ and 51 (32%) ER-. 8 pts discontinued tx (6 due to disease progression, 2 due to toxicity). 49% of pts had a pCR (RCB-0), 14% RCB-I, 26% RCB-II and 11% RCB-III. Higher rates of RCB-0 were seen in ER- (65%) versus ER+ (42%). ITH-HER2 was detected in 10% (16/157) of evaluable cases. No pCR was observed among cases classified as heterogeneous (RCB-I 25%, RCB-II 25%, RCB-III 50%). The study met its primary endpoint by demonstrating a significant association between ITH-HER2 and pCR stratified by ER status (p < .0001). Secondary analysis also demonstrated a significant association between ITH-HER2 and pathologic response defined as RCB 0 or I (OR = 5.6, p = 0.004). Exploratory analysis revealed higher rates of RCB-0 among tumors centrally classified as HER2 3+ (56% [66/118]) versus HER2 2+ (27% [10/37]), (OR = 3.4, p = 0.002). The association of ITH-HER2 and pCR was maintained when stratifying by ER status and HER2 IHC (2+ vs. 3+), (p = 0.002). Conclusions: ITH-HER2 assessed by routine pathology evaluation is a strong predictor of pCR to a dual-HER2 targeted therapy regimen. If validated, ITH-HER2 may need to be considered in selection of pts for HER2-targeted regimens without chemotherapy in the curative setting. Clinical trial information: NCT02326974.

1093 Background: The survival outcomes of postmenopausal women with invasive lobular carcinoma (ILC) are similar to invasive ductal carcinoma (IDC) when treated with aromatase inhibitor, but inferior when treated with tamoxifen. We sought to investigate the survival outcomes of premenopausal ILC when compared to IDC using a population-based analysis. Methods: We used Surveillance, Epidemiology, and End Results data (SEER) between 1990 to 2015 to identify premenopausal patients (defined as < 50 years old), diagnosed with stage I to III IDC or ILC. Breast Cancer Specific Survival (BCSS) was assessed using log-rank test and piecewisecox models. Annual hazard of BCCS for hormone receptor positive (ER+) ILC and ER+ IDC were calculated from year 0 to 20 and defined as the proportion of patients with a BCSS event during a 1-year interval. Results: The study includes a total of 170,352 pts diagnosed with either IDC (n = 158,733) and ILC (n = 11,619). 71% of IDC and 95% of ILC pts were ER+. Median age was 44 years old and median follow up was 90 months(IQR 40-151 months). Survival analysis revealed a significant time-dependent effect of histology for BCSS (p < .0001). When compared to IDC, ILC pts had better BCSS in the first 10 years after diagnosis (HR 0.73, 95% CI 0.68-0.78), but worse BCSS outcome after year 10 (HR 1.80, 95% CI 1.59- 2.03). Similar results were observed when adjusting for ER status, histologic grade and stage on multivariate analysis. Among pts ≤ 35 years old(n = 371 ILC; 18086 IDC) survival analysis revealed a non-significant trend towards inferior outcome for ILC compared to IDC throughout the whole follow-up period (HR = 1.2 95% CI 0.96-1.52). Annual hazard of BCCS events showed a peak at year 5 for both IDC and ILC. In the subset of IDC, we noticed a decreasing hazard of BCSS from years 6 through 20. By contrast, in the subset of ILC, we observed higher frequencies of BCSS from years 6-20 when compared to IDC (p < 0.0001). Conclusions: In this population-based analysis, premenopausal ILC had worse BCSS estimates when compared to premenopausal IDC. This is explained by a higher incidence of late events in the subset of ILC when compared to IDC.

BACKGROUND: PIK3CA mutations (mt) represent one of the most common gene aberrations occurring in breast cancer (BC). Despite their high prevalence, the mechanisms underlying prognosis in PIK3CA mutated BC remain largely unknown. METHODS: Seven datasets of primary BC patients were compiled comprising 1030 patients with available PIK3CA genotype and whole genome gene expression data. Overall survival data were available for 669 patients, 502 were ER-positive patients. We evaluated whether genes of interest (ESR1, HER2, MET, MYC, TP53, FGFR1) and previously published gene signatures (GS) of proliferation (AURKA, CIN70, GGI, Gene70), stroma (PLAU, DCN), and kinase signalling pathways (IGF1, SRC, PTEN, RAS, MAPK), were associated with PIK3CA genotype using ROC curve and t-tests as well as clinicopathologic parameters using chi-square and Mann-Whitney test. Survival and interactions with genotype was evaluated using Cox regression analyses, stratified by dataset. RESULTS: A total of 1030 cases were pooled for analysis. PIK3CA mt were found in 30.4% (314/1030) of cases in our cohort. PIK3CA mutations were significantly associated with positive ER status (p CONCLUSIONS: This is the largest analysis to combine gene expression and PIK3CA genotype. PIK3CA genotype was not significantly associated with survival in this cohort. There was no interaction between known prognostic GS reflecting proliferation and genomic instability and genotype implying that additional hits are necessary for PIK3CA mutated tumors to develop an aggressive, proliferative phenotype. In contrast, upregulation of MET was associated with a poor prognosis in only PIK3CA-mutated tumours suggesting a possible biomarker and rationale combination with PI3K inhibitors. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-11-02.