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5589 Background: Indoleamine 2,3-dioxygenase 1 (IDO1) allows tumor escape through kynurenine production, which induces regulatory T cells and suppresses effector T-cell proliferation. NIVO, an anti-PD-1 inhibitor can upregulate IDO1, supporting the rationale for combining NIVO with IDO. We report results of NIVO as monotherapy and in combination with IDO inhibitor BMS-986205 in the treatment of pts with recurrent EC. Methods: In this single-institution, randomized phase 2 study, eligible pts must have received 1-4 prior lines of chemotherapy and have measurable disease by RECIST v 1.1. All EC histologies, including carcinosarcoma, were allowed. Pts with microsatellite insufficient (MSI-H) or mismatch repair (MMR)-deficient tumors were excluded. Pts were randomized to NIVO 480mg IV every 4 weeks (wks) with or without IDO 100mg orally daily. Primary endpoints were Overall Response Rate [ORR = Complete Response (CR) + Partial Response (PR)] by RECIST v 1.1. Secondary objectives were duration of response (DOR), median progression free survival (mPFS), PFS rate at 24 wks (PFS24wks) and safety. Overall survival (OS) was also evaluated. Results: Between 10/2019 and 11/2021, pts were randomized to receive either NIVO (n = 12) or NIVO + IDO (n = 12). Median age was 67 years (range 48-82) and median number of prior lines of therapy was 2 (range 1-3). Histologies included serous (n = 5, 21%), endometrioid (n = 10, 42%), clear cell (n = 1, 4.2%), carcinosarcoma (n = 6, 25%), undifferentiated (n = 1, 4.2%), and mucinous (n = 1, 4.2%). In the NIVO + IDO arm, 1 pt achieved partial response (8.3%, CI: 0.9-100%) with DOR of 17.6 months. In the NIVO arm, no responses were observed. Efficacy outcomes are summarized in the table. Treatment-related adverse events (TRAEs) grade ≥ 3 in the NIVO arm included acute kidney injury (n = 1, 8.3%), hypokalemia (n = 1, 8.3%), and thromboembolic event (n = 1, 8.3%). In the NIVO + IDO arm, TRAEs grade ≥ 3 included fatigue (n = 1, 8.3%), and elevated liver function (n = 1, 8.3%). No TRAEs led to study-drug interruption or dose reductions. Conclusions: NIVO monotherapy and in combination with IDO showed acceptable safety in pts with recurrent EC. NIVO in combination with IDO showed ORR of 8.3%. No responses were observed with NIVO monotherapy. The trial closed to accrual due to lack of observed clinical efficacy. Clinical trial information: NCT04106414. [Table: see text]

5583 Background: EC and a subset of OVCA are associated with high rates of dMMR and are responsive to PD-1 blockade. It is unknown what additional biomarkers beyond dMMR may enrich for benefit in these patients (pts). Methods: This was an investigator-initiated, single-arm, phase II study. Eligible pts had recurrent EC or OVCA that met one of the following criteria: 1) dMMR, as determined by immunohistochemical loss of expression of 1+ MMR genes; 2) MSI-H, as determined by next generation sequencing (MSK-IMPACT); or 3) hypermutated, defined as 20+ non-synonymous somatic mutations. Pts received nivo 240mg IV every 2 weeks or 480mg IV every 4 weeks until toxicity or progression. The co-primary endpoints were 1) the progression-free survival (PFS) rate at 24 weeks (PFS24) and 2) the objective response rate (ORR) by RECIST v1.1. The study was designed using Simon’s two-stage design, with a sample size of 40 pts based on a promising ORR of 25% with a type I error rate of 0.025 and a type II error rate of 0.05. Overall survival (OS), PFS and duration of response (DOR) were calculated using the method of Kaplan-Meier. Adverse events (AEs) were graded per CTCAE and tabulated. Biomarker analyses on the available archival tissue were performed using multiplex immunofluorescence (mIF) labeling for CD8, PD-1, TOX, PD-1, PD-L1, and FoxP3. Quantification of immune phenotypes and interaction studies between CD8+ T cells and PD-L1+ cells was performed in HALO. Results: Between 9/2017 and 5/2021, 35 pts were enrolled; the study closed early due to slow accrual. The median duration of follow-up was 33.2 months. The median age was 64 years (range 36-87); 82% of pts were white, 54% had high grade EC, and 65% had confirmed MLH1 hypermethylation. The ORR was 57.1% (97.5% CI 39.4-100%) [37% PR, 20% CR]. The PFS24 was 62.9% and median PFS was 26.7 months (95% CI 4.9-NE). Neither median DOR nor OS was reached. OS at 1 year was 76.4% (95% CI 58.2-87.4%). The ORR in patients with MLH1 hypermethylation was 52%; 4 of 5 patients with confirmed germline MMR alterations had a response by RECIST. AEs were consistent with the reported literature. Notable treatment related AEs included Grade 4 myocarditis with associated grade 4 AV block, grade 2 extraocular paresis, grade 3 Type 1 diabetes mellitus, and grade 3 elevations in AST/ALT. On mIF analysis, PD-L1 expression did not distinguish responders from non-responders, though interaction between CD8+ T cells and PD-L1+ cells was associated with CR/PR. Increase in relative fraction of dysfunctional CD8+ T cells (characterized by CD8+TOX+PD-1+ phenotype) was also associated with CR/PR. Conclusions: Nivo is an effective and tolerable treatment option for patients with MMR-D/MSI-H or hypermutated EC or OVCA. Presence of dysfunctional CD8+ T cells in the tumors was associated with response, while expression of PD-L1 was not predictive. Clinical trial information: NCT03241745.

e14520 Background: Mismatch repair deficient (MMRd) tumors are highly sensitive to checkpoint blockade (CPB) in patients with metastatic disease regardless of tumor type. However, the efficacy of CPB in the adjuvant setting is unknown, especially since MMRd is considered a favorable biomarker for most resected tumor types. Circulating tumor DNA (ctDNA) could be used to screen for patients at high risk for recurrence following surgery or adjuvant chemotherapy and identify patients (pts) that would most benefit from CPB. Methods: To assess the frequency of ctDNA in the resected MMRd population, we prospectively screened pts with MMRd tumors who completed standard perioperative chemotherapy and surgery (NCT03832569). DNA from resected tumors and matched postoperative plasma was sequenced for the presence of somatic mutations. Patients were considered to have minimal residual disease (MRD) when mutations were identified in tumor and found to be identical to those in matched plasma DNA. Somatic tissue mutations were assessed using MSK-IMPACT and ctDNA was assessed using FoundationOne, Guardant360 or MSK-ACCESS. Results: A total of 86 pts were screened for the presence of MRD. These represented 7 tumor types with colorectal (63%), endometrial (16%) and esophagogastric (13%) being the most common. The majority of pts were stage III (49%). MRD was detected in 18% of cases (14 of 79). Among the MRD negative group (n=62), only one pt developed disease recurrence. Three samples failed ctDNA analysis for technical reasons. Conclusions: MRD was identified in 18% of resected MMRd tumors using ctDNA analysis, suggesting this to be a feasible tumor agnostic approach to test the efficacy of CPB in a pts at high-risk for recurrence. Future studies will assess the impact of CPB in MRD positive MMRd tumors.[Table: see text]

TPS6098 Background: Onapristone extended release (ER) is a type I full progesterone antagonist that inhibits progesterone mediated PR activation and stabilizes PR association with corepressors. Onapristone has shown activity across multiple preclinical models of hormonally driven cancer. A phase I dose escalation study of onapristone ER in PR+ breast, endometrial and ovarian cancer patients found all doses tested to be well tolerated, with 50mg PO BID determined to be the recommended phase 2 dose (RP2D). GCT (98% of cases PR+), LGSOC (58% of cases PR+) and EEC (67% of cases PR+) are hormonally driven cancers which generally have poor responses to chemotherapy and limited treatment options in the recurrent setting. Methods: This is an open-label, investigator-initiated basket study of onapristone ER in patients with PR+ recurrent GCT, LGSOC, or EEC currently enrolling patients at Memorial Sloan Kettering Cancer Center in NY, USA (NCT03909152). The primary objective is to evaluate the efficacy, in terms of response rate by RECIST 1.1 criteria, within 36 weeks of treatment. Eligible patients must have received at least 1 prior line of chemotherapy, have measurable disease by RECIST 1.1 criteria, and have tumor tissue collected within 3 years prior to enrollment with PR expression ≥ 1% by IHC. Patients are allowed to have unlimited additional prior lines of chemotherapy, biologic therapy, immunotherapy or hormonal therapy. Enrolled patients are treated with onapristone ER 50mg PO BID until time of progression or intolerable toxicity. The 3 disease cohorts are currently enrolling to Stage I in parallel with expansion from stage I to stage II planned when the prespecified response criteria are met for each cohort as described in the table below. Clinical trial information: NCT03909152. [Table: see text]

5513 Background: Adavosertib (AZD1775; A), a highly selective WEE1 inhibitor, demonstrated activity and tolerability in combination with carboplatin (C) in primary PROC. This study (NCT02272790) assessed the objective response rate (ORR) and safety of A in PROC. Methods: Pts with recurrent RECIST v1.1 measurable PROC received A with C, gemcitabine (G), weekly paclitaxel (P), or pegylated liposomal doxorubicin (PLD) in 3- (C) or 4-week (G, P, PLD) cycles (Table). Tumor assessments were performed every 2 cycles until disease progression. Primary objective: ORR; other objectives: disease control rate (DCR), progression-free survival (PFS) and safety. Results: In the 94 pts treated (median treatment duration 3 months; range 0–16 months), outcomes were greatest with A (weeks [W]1–3) + C (Table), with ORR of 67% and median PFS (mPFS) of 10.1 months for this cohort. Most common grade ≥3 treatment-emergent adverse events (TEAEs) are shown in the Table, with hematologic toxicity most notable with A (W1–3) + C. TEAEs led to A dose interruptions, reductions and discontinuations in 63%, 30% and 13% of the whole cohort, respectively. A possible positive relationship between CCNE1 amplification and response warrants further investigation. Conclusions: A shows preliminary efficacy when combined with CT. Pts receiving A (W1–3) + C showed greatest benefit. The increased but not unexpected hematologic toxicity is a challenge and could be further studied to optimize the dose schedule and supportive medications. Clinical trial information: NCT02272790. [Table: see text]

5582 Background: Monoclonal antibodies Durvalumab (D) and Tremelimumab (T) inhibit binding of programmed cell death ligand 1 (PDL1) to PD1 and inhibit activation of cytotoxic T-lymphocyte-associated protein 4 (CTLA4), respectively, resulting in improved tumor immunosurveillance. There is rationale to study D and DT based on recent genomic and tumor microenvironment evaluation of endometrial cancer (EC). Methods: Eligible patients (pts) were randomized to D or DT. Pts received D 1500 mg intravenously (IV) every 4 weeks (wks). DT therapy pts received D 1500 mg IV every 4 wks and T 75 mg IV every 4 wks for 4 cycles, followed by D 1500 mg IV every 4 wks until progression or unacceptable toxicities. Pts were stratified by histology with 10 carcinosarcoma or MSI-H EC pts per arm. Efficacy assessments were every 8 wks and treatment related adverse events (TRAEs) were assessed per CTCAE v.4.03. The primary endpoint was overall response rate (ORR) by RECIST v1.1. Descriptive statistics and 90% one sided CI are reported. Progression free survival (PFS) rate at 24 wks (PFS24wks) was estimated by Kaplan Meier method. Results: At planned interim analysis, 56 pts were enrolled (28 per arm). 15 pts: carcinosarcoma, 15 pts: endometrioid (3: Gr1), 14 pts: serous, and 12 pts: other histology. 5(9%) pts: MSI-H, 48(86%) pts: microsatellite stable (MSS), 3(5%): unknown. 2 pts were excluded due to early death. 27 pts per arm were evaluable for efficacy. In the D arm: 1 pt had complete response (CR)(MSS) and 3 pts had a partial response (PR) (2:MSS, 1:MSI-H) with an ORR of 14.8% (CI: 6.6-100%). The median PFS was 7.6 wks and PFS24wks was 13.3% (CI 6.1-100%). Median duration of response (DOR) was 16 wks in the D arm. In the DT arm, 2 pts achieved CR (1:MSI-H, 1:MSS) and 1 had PR (MSS). The ORR was 11.1% (CI: 4.2-100%). Median PFS was 8.1 wks, PFS24wks was 18.5% (CI 10.1-100%) and DOR was 8 wks. Grade 3 TRAEs occurred in 2 (7%) pts in D and 9 (32%) pts in DT. Grade 4 TRAEs occurred 1 (4%) pt in D and 3 (11%) pts in DT. 2 pts discontinued due to a TRAE. Most common TRAEs in total were fatigue (23%), diarrhea (20%), nausea (14%), vomiting (13%) and pruritis (11%). Conclusions: D and DT show modest activity in EC. No new safety signals were identified. Second stage accrual is ongoing. Clinical trial information: NCT03015129.

Purpose Dose-dense (dd) doxorubicin and cyclophosphamide (AC) followed by paclitaxel (P) is superior to every 3-weekly AC followed by P. Given the demonstrated cardiac safety for trastuzuamb (T) with conventionally scheduled AC followed by P, we tested the safety of dd AC followed by P with T. The primary end point was cardiac safety, and the secondary end points were time to recurrence and overall survival. Methods Patients with HER-2/neu immunohistochemistry (IHC) 3+ or fluorescent in situ hybridization (FISH)-amplified breast cancer and baseline left ventricular ejection fraction (LVEF) of ≥ 55% were enrolled, regardless of tumor size or nodal status. Treatment consisted of AC (60/600 mg/m2) × 4 followed by P (175 mg/m2) × 4 every 2-weekly with pegfilgrastim (6 mg on day 2) + T ×1 year. LVEF by radionuclide scan was obtained at baseline, at months 2, 6, 9, and 18. Results From January 2005 to November 2005, 70 patients were enrolled. The median age was 49 years (range, 27 to 72 years); median LVEF at baseline was 68% (range, 55% to 81%). At month 2 in 70 of 70 patients, the median LVEF was 67% (range, 58% to 79%); at month 6 in 67 of 70 patients, it was 66% (range, 52% to 75%); at month 9 in 68 of 70 patients, it was 65% (range, 50% to 75%); and at month 18 in 48 of 70 patients, it was 66% (range, 57% to 75%). As of December 1, 2007, the median follow-up was 28 months (range, 25 to 35 months). One patient (1%) experienced conestive heart failure (CHF). There were no cardiac deaths. Conclusion Dose-dense AC followed by P/T followed by T is feasible and is not likely to increase the incidence of cardiac events compared to established regimens.

Purpose To determine the immediate and long-term effects of true acupuncture versus sham acupuncture on hot flash frequency in women with breast cancer. Patients and Methods Seventy-two women with breast cancer experiencing three or more hot flashes per day were randomly assigned to receive either true or sham acupuncture. Interventions were given twice weekly for 4 consecutive weeks. Hot flash frequency was evaluated at baseline, at 6 weeks, and at 6 months after initiation of treatment. Patients initially randomly assigned to the sham group were crossed over to true acupuncture starting at week 7. Results The mean number of hot flashes per day was reduced from 8.7 (standard deviation [SD], 3.9) to 6.2 (SD, 4.2) in the true acupuncture group and from 10.0 (SD, 6.1) to 7.6 (SD, 5.7) in the sham group. True acupuncture was associated with 0.8 fewer hot flashes per day than sham at 6 weeks, but the difference did not reach statistical significance (95% CI, −0.7 to 2.4; P = .3). When participants in the sham acupuncture group were crossed over to true acupuncture, a further reduction in the frequency of hot flashes was seen. This reduction in hot flash frequency persisted for up to 6 months after the completion of treatment. Conclusion Hot flash frequency in breast cancer patients was reduced following acupuncture. However, when compared with sham acupuncture, the reduction by the acupuncture regimen as provided in the current study did not reach statistical significance. We cannot exclude the possibility that a longer and more intense acupuncture intervention could produce a larger reduction of these symptoms.

1037 Background: The combination of taxanes with HP for first line treatment of HER2-positive MBC is associated with improved progression-free (PFS) and overall survival (OS). Treatment per physician’s choice with anti-HER2 therapy after second line therapy is associated with a median PFS of 3 months. While continued use of H in therapeutic combinations after progression on H-based therapy is standard, the efficacy of continuing HP-based treatment after progression on P-based therapy is unknown. Methods: This is a single arm phase II trial of G with HP. Eligible patients (pts) had HER2-positive (IHC 3+ or FISH > 2.0) MBC with prior HP-based treatment and ≤ 3 prior chemotherapies. Pts received G (1200 mg/m2) on days 1 and 8 of a q 3 week (w) cycle, and H (8 mg/kg load → 6 mg/kg) and P (840 mg load → 420 mg) q3w. The primary endpoint is PFS at 3 months. Secondary endpoints include OS, safety and tolerability. An exploratory endpoint is to compare PFS by RECIST criteria versus 18-F FDG-PET response criteria. The study therapy will be considered successful if at least 27/45 (60%) patients are progression free at 3 months. Results: As of 1-27-17, 41 of 45 pts are enrolled; 34 are evaluable at 3 months and 7 have not had 3-month evaluation. At 3 months, 26/34 (76%) are progression free (1 CR, 8 PR, 17 SD); 8 pts progressed. There are no cardiac or febrile neutropenic events to date. 4 pts required G dose reduction (3 grade 3 neutropenia and 1 grade 3 vomiting) and the study was amended to lower initial G dose to 1000 mg/m2. Conclusions: The preliminary 3 month-PFS is 76% in evaluable pts (95% CI 60% to 88%). The updated 3 month-PFS results will be presented. Continuation of P beyond progression is associated with apparent clinical benefit. A randomized trial is justified to confirm this clinically important observation. Clinical trial information: NCT02252887.

TPS5602Background: Approximately 75% of women with epithelial ovarian cancer (OC) present with advanced disease. The majority of these women will ultimately recur and require life-long treatment fo...

607 Background: We previously reported results of the phase II breast cancer (BC) trial of weekly paclitaxel (T), trastuzumab (H) and pertuzumab (P) with its primary endpoint of 6-month (mo) progre...

590 Background: CMF (C 600 mg/m2, M 40 mg/m2, F 600 mg/m2) is an option for adjuvant therapy for patients with low risk early stage breast cancer. DD regimens as predicted by mathematical models of cancer growth and treatment response are superior. We previously demonstrated the safety of DD EC (epirubicin/cyclophosphamide) followed by paclitaxel at 10–11 day (d) intervals. We investigated the feasibility of administering DD adjuvant CMF every 14 d and then every 10–11 d in a 2-stage phase II trial. Methods: An initial cohort (A) was treated q 14 d with PEG-filgrastim (Neulasta) support. A second cohort (B) was treated every 10–11 d with filgrastim/Neupogen x 5 d and then, based on feasibility, modified (cohort C) to use 7 d filgrastim. The primary end point was feasibility defined as having ANC > 1.5 x 103/uL on day 1 of planned treatment for all 8 cycles with no grade 3 or higher non-hematologic toxicity. All three cohorts were tested using a Simon's two-stage optimal design with type I and type II errors set at 10%. This design would effectively discriminate between true tolerability (as protocol-defined) rates of< 60% and> 80%. Cohort A: 38 pts with early stage breast cancer were accrued from 3/2008 though 6/2008. Cohort B: 7 pts were accrued from June 2008 through August 2008. Cohort C: Is still open with 16 pts accrued from August 2008 through December 5, 2008. Results: Median age 51: range 38 to 78. Cohort A: 29/38 pts completed 8 cycles of CMF. The regimen was considered feasible. 2 other pts completed 7 cycles and were withdrawn for depression and grade 2 transaminitis. The 7 other pts completed between 1 and 6 cycles of CMF were withdrawn as follows: 3 personal, 1 (grade 3) bone pain, 2 allergy unrelated to CMF, and 1 seizure. Cohort B: 7 pts were accrued. 6 out of 7 pts could not complete 8 cycles of chemotherapy secondary to neutropenia and 1 secondary to grade 3 ALT elevation. Cohort C: Accrual has not been completed. 16 pts are currently enrolled. Conclusions: Dose dense adjuvant CMF is feasible at 14 d intervals with PEG-filgrastim support. Adjuvant CMF every 10–11 days with filgrastim given for 5 days beginning day 2 is not feasible. Accrual is ongoing for CMF at 10–11 days with filgrastim x 7 days. Updated results will be available for Cohort C. [Table: see text]

582 Background: DD q 2 weekly (w) AC → T is superior to conventionally scheduled (cs) AC → T and safe w/long follow-up (Hudis et al, SABCS 2005). With q 3 wk AC, adjuvant (adj) H is safe and effective (Romond et al and Perez et al, NEJM 2005). We therefore tested DD q 2 w AC → T + H × 1 year (y) as adj treatment (Rx) of patients (pts) with HER2/neu (+) BCA to determine cardiac safety. Based on the reported cardiac event (CE) rate of ≤ 4% in the randomized trials using cs chemotherapy (CRx) + H, we evaluated DD q 2 w AC → T + H with a 1° endpoint of cardiac safety defined as discontinuation (DC) of H due to 1) cardiac death or 2) congestive heart failure (CHF). The 2° endpoint is time to recurrence and overall survival. Methods: Pts with HER2/Neu IHC 3+ or FISH-amplified BCA were enrolled, regardless of tumor size or nodal status. Rx consisted of AC at 60/600 mg/m2 × 4 → T at 175 mg/m2 × 4 q 2 w w/pegfilgrastim 6 mg on d 2 + H × 1 y. Multi-gated radionuclide angiography scan (MUGA) is obtained at baseline and at months (mo) 2 (after AC × 4), 6 (after T × 4), 9, and 18. Pts w/baseline LVEF of ≥ 55% and w/o cardiac illnesses are eligible. Pts w/significant (sig) asymptomatic (asx) LVEF ↓ after DD AC based on mo 2 MUGA did not receive H, and pts w/sig asx LVEF ↓ during H had it DC’d. If the CE rate is > 4%, Rx is deemed not feasible. Results: From January 4, 2005 to November 1, 2005, 70 pts were enrolled. Median (med) age is 49 years (range, 27–72). Forty one of 70 pts (60%) had node (+) BC and 27/70 pts (40%) had (-) nodes. Med baseline LVEF is 68% (range, 55%-81%). As of January 9, 2005, all pts had mo 2 MUGA after DD AC and there is no sig LVEF ↓ and the med LVEF is 67% (range, 58%-79%). To date 39 pts had mo 6 MUGA w/med LVEF of 66% (range, 56%-75%) and one pt had a sig asx LVEF ↓ from baseline of 74% to 56%; H was DC’d. Twenty-three pts had mo 9 MUGA w/a med LVEF of 64% (range, 57%-69%). One patient had clinical CHF at mo 4 w/EF of 45% and improved sig w/cardiac medications. One had pneumonitis during radiation (RT). One had atrial fibrillation w/pericarditis after completion of RT. Discussion: DD AC → T + H appears to have an acceptable cardiac toxicity profile w/1/70 pts having a CE. Updated cardiac safety data will be presented. [Table: see text]