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Background CDK4/6 inhibitors (CDK4/6i) in combination with endocrine therapy (ET) have a well-established role in the management of hormone receptor-positive (HR+)/HER2- metastatic breast cancer (MBC). The benefit of continuing CDK4/6i beyond progression in combination with a different ET has not been confirmed. Preclinical data suggest synergy between CDK4/6i and PD-L1 inhibition. The PACE trial prospectively evaluates whether continuation of the CKD4/6i palbociclib beyond progression on prior CDK4/6i and aromatase inhibitor (AI), with a change in ET to fulvestrant, improves outcomes beyond change to fulvestrant alone, as well as explores the activity of the palbociclib, fulvestrant, and avelumab triplet. Methods PACE is a multicenter randomized open-label investigator-initiated phase II trial, open at 11 U.S. sites. Eligible patients (pts) had HR+/HER2- evaluable MBC with prior progression on AI and any CDK4/6i after > 6 months (mo) of therapy in the MBC setting, or during/within 12 mo in the adjuvant setting, with no more than 1 prior line of chemotherapy for MBC. Pts were randomized 1:2:1 to fulvestrant alone (F); fulvestrant and palbociclib (F+P); or fulvestrant, palbociclib, avelumab (F+P+A), with tumor assessments every 8 weeks. Blood for circulating tumor DNA (ctDNA) analysis was collected at baseline, at times of tumor assessments, and at progression. The primary objective was to evaluate progression-free survival (PFS) with F+P vs F; secondary objectives included PFS with F+P+A vs F, objective response rate (ORR) in all arms, and safety. A sample size of 220 patients was planned to provide 80% power to detect an improvement in PFS with HR 0.6154 with F+P vs F (6.5 vs 4 mo; α(1)=0.05). Results A total of 220 pts were randomized from 9/2017-2/2022 (F: n=55, F+P: n=111, F+P+A: n=54); median age 57 years (range 25-83), 85% non-Hispanic (7.7% non-Hispanic black), 8.6% Hispanic, 6.4% unknown. 40% had de novo MBC, 60% had visceral disease, and 14% bone-only disease. 16% had 1 prior line of chemotherapy for MBC, 90% had received prior palbociclib, 4.5% ribociclib, 4.1% abemaciclib, 1.4% palbociclib and ribociclib. Pts entered the trial after a median 19 mo of prior CDK4/6i plus AI (interquartile range 12-31 mo). A total of 10 (5%) pts received protocol therapy as first line ET for MBC, 169 (77%) as second line, and 41 (17%) as beyond second line. 88% entered the trial directly after progression on CDK4/6i. After a median follow-up of 24 mo, 18 pts remained on protocol treatment. PFS was not improved with F+P vs F (median 4.6 vs 4.8 mo; HR=1.11, 90% CI 0.79-1.55; 2-sided p=0.62). Median PFS was 8.1 mo with F+P+A (HR=0.75 vs F, 90% CI 0.50-1.12; 2-sided p=0.23). ORR was 7.3% (90%CI 1.5-13.0) with F, 9.0% F+P (4.5-13.5%) and 13.0% F+P+A (5.4-20.5%). No new safety signals have been observed. Analysis of ctDNA panel sequencing encompassing 70 genes from 184 baseline samples, including correlation with known and hypothesized resistance genes, will be presented. Conclusions For ER+/HER2- breast cancer, combining palbociclib with fulvestrant beyond progression on prior CDK4/6i and AI did not significantly improve PFS compared with using fulvestrant alone. The observed longer PFS when a PD-L1 inhibitor was added to fulvestrant plus palbociclib is an intriguing signal in this ER+ population. Translational studies of blood and tumor tissue are ongoing and will be presented. Citation Format: Erica L. Mayer, Yue Ren, Nikhil Wagle, Reshma Mahtani, Cynthia Ma, Angela DeMichele, Massimo Cristofanilli, Jane Meisel, Kathy D. Miller, Trevor Jolly, Elizabeth Riley, Rubina Qamar, Priyanka Sharma, Sonya Reid, Natalie Sinclair, Meredith Faggen, Caroline Block, Naomi Ko, Ann Partridge, Wendy Y. Chen, Michelle K. DeMeo, Victoria Attaya, Amanda Okpoebo, Yuan Liu, Eric Gauthier, Harold Burstein, Meredith Regan, Sara Tolaney. GS3-06 Palbociclib After CDK4/6i and Endocrine Therapy (PACE): A Randomized Phase II Study of Fulvestrant, Palbociclib, and Avelumab for Endocrine Pre-treated ER+/HER2- Metastatic Breast Cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr GS3-06.

Background Combination irinotecan and cetuximab is approved for irinotecan-refractory metastatic colorectal cancer (mCRC). It is unknown if adding bevacizumab improves outcomes. Patients and Methods In this multicenter, randomized, double-blind, placebo-controlled phase II trial, patients with irinotecan-refractory RAS-wildtype mCRC and no prior anti-EGFR therapy were randomized to cetuximab 500 mg/m2, bevacizumab 5 mg/kg, and irinotecan 180 mg/m2 (or previously tolerated dose) (CBI) versus cetuximab, irinotecan, and placebo (CI) every 2 weeks until disease progression or intolerable toxicity. The primary endpoint was progression-free survival (PFS). Secondary endpoints included overall survival (OS), objective response rate (ORR), and adverse events (AEs). Results The study closed early after the accrual of 36 out of a planned 120 patients due to changes in funding. Nineteen patients were randomized to CBI and 17 to CI. Baseline characteristics were similar between arms. Median PFS was 9.7 versus 5.5 months for CBI and CI, respectively (1-sided log-rank P = .38; adjusted hazard ratio [HR] = 0.64; 95% confidence interval [CI], 0.25-1.66). Median OS was 19.7 versus 10.2 months for CBI and CI (1-sided log-rank P = .02; adjusted HR = 0.41; 95% CI, 0.15-1.09). ORR was 36.8% for CBI versus 11.8% for CI (P = .13). Grade 3 or higher AEs occurred in 47% of patients receiving CBI versus 35% for CI (P = .46). Conclusion In this prematurely discontinued trial, there was no significant difference in the primary endpoint of PFS between CBI and CI. There was a statistically significant improvement in OS in favor of CBI compared with CI. Further investigation of CBI for the treatment of irinotecan-refractory mCRC is warranted. Clinical Trial Registration: NCT02292758

Background: Platinum agents induce DNA crosslinking and cause accumulation of genotoxic stress, which leads to immune activation via IFN-γ signaling, making the combination with nivolumab (PD-1 antibody) an attractive strategy to enhance the benefit of either agent alone in metastatic triple-negative breast cancer (mTNBC). Methods: In this phase II open-label, investigator-initiated, multicenter trial, patients with unresectable locally advanced or mTNBC treated with 0-1 prior lines of chemotherapy in the metastatic setting were randomized 1:1 to carboplatin (AUC 6) with or without nivolumab (360 mg) IV every 3 weeks. Stratification factors included: germline BRCA (gBRCA) status, prior neo/adjuvant platinum, and number of prior lines of metastatic therapy. After approval of PD-L1 inhibition for mTNBC, the study was amended to include first-line mTNBC only and PD-L1 status was added as a stratification factor. Patients randomized to carboplatin alone were allowed to crossover at progression to receive nivolumab (+ nab-paclitaxel post-amendment). The primary objective was to compare progression-free survival (PFS) per RECIST 1.1 criteria of carboplatin with or without nivolumab in first-line mTNBC in the intent-to-treat (ITT) population. Key secondary objectives were objective response rate (ORR), overall survival (OS), clinical benefit rate, and duration and time to objective response. PD-L1 status was confirmed centrally using the SP142 Ventana assay (positive, ≥1% IC). Paired research biopsies at baseline, on-treatment and at progression were performed, if safely accessible. The trial closed to accrual prior to reaching target accrual due to approval of PD-1 inhibition in combination with platinum-based chemotherapy for PD-L1+ mTNBC. Results: Between 1/30/2018 and 12/9/2020, 78 patients enrolled. Three patients did not receive protocol treatment, and the safety analysis was conducted among the 75 that received any treatment; 37 received carboplatin + nivolumab (Arm A), 38 received carboplatin alone (Arm B). Median age was 59.1 yrs (range: 25.4-75.8). Four patients (5.3%) had a known gBRCA1/2 mutation. Sixty-two (82.7%) patients received 0 prior lines (ITT population) and 13 (17.3%) 1 prior line of metastatic therapy. Sixty-seven patients (89.3%) experienced any grade ≥2 treatment-related adverse event (AE). The most frequent AE were platelet count decrease (n=40; 53.3%), anemia (n=36; 48.0%), neutrophil count decrease (n=33; 44.0%) and fatigue (n=24; 32.0%). Grade 3/4 AE were observed in 46 (61.3%) patients, and there was one grade 5 AE (COVID19 pneumonia). Any grade ≥2 immune-related AE (irAE) were observed in 25 of the 37 (67.6%) patients treated with carboplatin + nivolumab. Grade 3/4 irAE were observed in 11 (29.7%) patients. In the ITT population (32 on Arm A; 30 on Arm B), median PFS was 4.2 months with carboplatin + nivolumab, and 5.5 months with carboplatin (stratified HR 0.98, 95% CI [0.51 - 1.88]; p=0.95). ORR was 25% vs. 23.3%, respectively. At a median follow-up of 23.5 months, median OS was 17.5 months vs. 10.7 months (stratified HR 0.63, 95% CI [0.32 - 1.24]; p=0.18). In patients with PD-L1+ mTNBC (13 on Arm A; 11 on Arm B), median PFS was 8.3 months and 4.7 months, respectively (stratified HR 0.63, 95% CI [0.21 - 1.89]; p=0.41). ORR was 23.1% vs. 27.3%, respectively. Median OS was 17.5 months vs. 9.6 months (stratified HR 0.59, 95% CI [0.20 - 1.75]; p=0.34). Conclusions: Addition of nivolumab to carboplatin in patients with previously untreated mTNBC, unselected by PD-L1 status, did not significantly improve PFS. A trend toward improved PFS and OS was observed in patients with PD-L1+ mTNBC. Tissue, blood and intestinal microbiome biomarker analyses are planned; bulk tumor and single-cell sequencing, and TCR sequencing in peripheral blood are ongoing. Clinical trial information: NCT03414684. Citation Format: Ana C Garrido-Castro, Noah Graham, Kevin Bi, Jihye Park, Jingxin Fu, Tanya Keenan, Edward Thomas Richardson, Ricardo Pastorello, Paulina Lange, Victoria Attaya, Robert Wesolowski, Natalie Sinclair, Zarah Lucas, Steve Lo, Nadine Tung, Meredith Faggen, Peter A Kaufman, Caroline C Block, Fred Briccetti, Madhavi Toke, Wendy Chen, Kai Wucherpfennig, Sascha Marx, Ye Tian, Judith Agudo, Jennifer L Guerriero, Stuart Schnitt, Nancy U Lin, Eric P Winer, Elizabeth A Mittendorf, Nabihah Tayob, Eliezer Van Allen, Sara M Tolaney. A randomized phase II trial of carboplatin with or without nivolumab in metastatic triple-negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-14-18.

Background In early trials, hypersensitivity reactions (HSRs) to paclitaxel were common, thus prompting the administration of antihistamines and corticosteroids before every paclitaxel dose. We tested the safety of omitting corticosteroids after cycle 2 during the paclitaxel portion of the dose‐dense (DD) doxorubicin‐cyclophosphamide (AC)–paclitaxel regimen. Patients, Materials, and Methods In this prospective, single‐arm study, patients who completed four cycles of DD‐AC for stage I–III breast cancer received paclitaxel 175 mg/m2 every 2 weeks for four cycles. Patients received a standard premedication protocol containing dexamethasone, diphenhydramine, and a histamine H2 blocker prior to the first two paclitaxel cycles. Dexamethasone was omitted in cycles three and four if there were no HSRs in previous cycles. We estimated the rate of grade 3–4 HSRs. Results Among 127 patients enrolled, 125 received more than one dose of protocol therapy and are included in the analysis. Fourteen (11.2%; 90% confidence interval, 6.9%–20.0%) patients had any‐grade HSRs, for a total of 22 (4.5%; 3.1%–6.4%) HSRs over 486 paclitaxel cycles. Any‐grade HSRs occurred in 1.6% (0.3%–5.0%), 6.5% (3.3%–11.3%), 7.4% (3.9%–12.5%), and 2.6% (0.7%–6.6%) of patients after paclitaxel cycles 1, 2, 3, and 4, respectively. Dexamethasone use was decreased by 92.8% in cycles 3 and 4. Only one patient experienced grade 3 HSR in cycles 3 or 4, for a rate of grade 3/4 HSR 0.4% (0.02%–2.0%) (1/237 paclitaxel infusions). That patient had grade 2 HSR during cycle 2, and the subsequent grade 3 event occurred despite usual dexamethasone premedication. A sensitivity analysis restricted to patients not known to have received dexamethasone in cycles 3 and 4 found that any‐grade HSRs occurred in 2.7% (3/111; 0.7%–6.8%) and 0.9% (1/109; 0.05%–4.3%) of patients in cycle 3 and 4, respectively. Conclusion Corticosteroid premedication can be safely omitted in cycles 3 and 4 of dose‐dense paclitaxel if HSRs are not observed during cycles 1 and 2. Implications for Practice Because of the potential for hypersensitivity reactions (HSRs) to paclitaxel, corticosteroids are routinely prescribed prior to each dose, on an indefinite basis. This prospective study, including 125 patients treated with 486 paclitaxel cycles, demonstrates that corticosteroids can be safely omitted in future cycles if HSRs did not occur during cycles 1 and 2 of paclitaxel and that this strategy reduces the use of corticosteroids in cycles 3 and 4 by 92.8% relative to current standard of care., To avoid hypersensitivity reactions, corticosteroids are routinely prescribed before each dose of paclitaxel. This article reports the results of a study that focused on whether corticosteroids could be safely omitted in later cycles of treatment if reactions did not occur during earlier cycles.

Background: The ATEMPT trial primary analysis found that one year of adjuvant trastuzumab emtansine (T-DM1) achieved a 3-year iDFS of 97.8% for patients with stage I HER2+ breast cancer, but was not associated with fewer clinically relevant toxicities (CRTs) compared with paclitaxel and trastuzumab (TH). In this end-of-study analysis, we report 5-year survival outcomes and correlative analyses from the trial. Methods: Patients with stage I centrally confirmed HER2+ breast cancer were randomly assigned 3:1 to adjuvant T-DM1 for one year or TH and received T-DM1 3.6 mg/kg IV every 3 weeks for 17 cycles or paclitaxel 80 mg/m2 IV with weekly trastuzumab IV followed by trastuzumab for 9 months. The co-primary objectives were to compare the incidence of CRTs between the 2 arms and to evaluate iDFS in patients receiving T-DM1. To investigate proteomic correlates of recurrence, spatial proteomic analyses were performed on samples from 13 patients experiencing iDFS events (cases) and 24 matched controls using the NanoString GeoMx Digital Spatial Profiler. The impact of HER2 heterogeneity on outcomes was investigated among 17 cases and 51 matched controls by fluorescence in-situ hybridization (FISH). HER2 genetic heterogeneity was assessed by scrutinizing the whole tumor area and defined as the occurrence of HER2 gene amplification in >5% but < 50% invasive tumor cells. The risk of recurrence was evaluated centrally with the HER2DX genomic assay from 225 primary tumor samples. Germline whole genome sequencing (WGS) was conducted among 55 patients experiencing T-DM1-induced thrombocytopenia and/or bleeding and 55 matched controls to identify genomic correlates for this side effect. Results: A total of 497 patients who initiated protocol therapy were included in this analysis (383 T-DM1 and 114 TH). After a median follow up 5.8 years, among patients receiving T-DM1 there were a total of 11 iDFS events, with 3 distant recurrences. The 5-year iDFS for T-DM1 was 97.0% (95% CI, 95.3-98.8%), the 5-year recurrence-free interval (RFI) was 98.6% (95% CI: 97.4-99.8%) and the 5-year overall survival (OS) for T-DM1 was 97.8 % (95% CI, 96.3-99.3%). Although the study was not powered to evaluate the efficacy of TH, among the 114 patients receiving TH, a total of 9 iDFS events were observed, including 2 distant events; the 5-year iDFS with TH was 91.3% (95% CI: 86.0-96.9%), 5-year RFI was 93.3% (95% CI: 88.6-98.2%) and 5-year OS was 97.9% (95% CI: 95.2-100%). A total of 56 samples were evaluable for heterogeneity analyses, among which 14% (n=8) harbored HER2 genetic heterogeneity. Spatial proteomic analyses found that NF1 (adjusted p=0.72 × 10-6) and CTLA-4 (adjusted p=0.15 × 10-3) were significantly upregulated in primary samples from cases, while cleaved caspase 9, CD25, GITR, ICOS, p53 and PD-L2 were significantly upregulated in controls (all with adjusted p< 0.05). Germline WGS found that the top gene associations with thrombocytopenia and thrombocytopenia or bleeding were ALMS1 (p=0,19 × 10-3) and APBA3 (p=0,23 × 10-3), respectively, although none reaching the threshold for genome wide significance. rs62143195 and rs114169776 were the top single nucleotide polymorphisms associated with thrombocytopenia and thrombocytopenia or bleeding, respectively. Data on the impact of HER2 heterogeneity and of HER2DX score on survival outcomes will be presented. Conclusion: With longer follow-up, adjuvant T-DM1 confirmed outstanding long-term outcomes among patients with stage I HER2+ breast cancer, demonstrating a 5-year RFI of 98.6%. Spatial proteomic analyses identified a potential association between NF1 and CTLA-4 expression with recurrence. Details on the impact of HER2 heterogeneity and HER2DX assay on prognosis will be presented. Citation Format: Paolo Tarantino, Nabihah Tayob, Chau T Dang, Denise Yardley, Steven J. Isakoff, Vicente Valero, Meredith Faggen, Therese Mulvey, Ron Bose, Douglas Weckstein, Antonio C. Wolff, Katherine Reeder-Hayes, Hope Rugo, Bhuvaneswari Ramaswamy, Dan Zuckerman, Lowell Hart, Vijayakrishna K. Gadi, Michael Constantine, Kit Cheng, Audrey Merrill Garrett, Paul K. Marcom, Kathy S. Albain, Patricia DeFusco, Nadine Tung, Blair Ardman, Rita Nanda, Rachel C. Jankowitz, Mothaffar Rimawi, Vandana Abramson, Paula R. Pohlmann, Catherine Van Poznak, Andres Forero-Torres, Minetta C. Liu, Kathryn Ruddy, Yue Zheng, Romualdo Barroso-Sousa, Adrienne Waks, Michelle K. DeMeo, Molly K. DiLullo, Giuseppe Curigliano, Harold Burstein, Ann Partridge, Eric Winer, Giuseppe Viale, Winnie Hui, Elizabeth A. Mittendorf, Bryan P. Schneider, Aleix Prat, Ian Krop, Sara Tolaney. Adjuvant Trastuzumab Emtansine Versus Paclitaxel plus Trastuzumab for Stage I HER2+ Breast Cancer: 5-year results and correlative analyses from ATEMPT (TBCRC033) [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr PD18-01.

To support shared decision-making, patient-facing resources are needed to complement recently published guidelines on approaches for surveillance mammography in breast cancer survivors aged ≥ 75 or with 10-year life expectancy. We created a patient guide to facilitate discussions about surveillance mammography in older breast cancer survivors.The "Are Mammograms Still Right for Me?" guide estimates future ipsilateral and contralateral breast (in-breast) cancer risks, general health, and the potential benefits/harms of mammography, with prompts for discussion. We conducted in-clinic acceptability testing of the guide by survivors and their clinicians at a National Cancer Institute-designated comprehensive cancer center, including two community practices. Patients and clinicians received the guide ahead of a clinic visit and surveyed patients (pre-/post-visit) and clinicians (post-visit). Acceptability was defined as ≥ 75% of patients and clinicians reporting that the guide (a) should be recommended to others, (b) is clear, (c) is helpful, and (d) contains a suitable amount of information. We also elicited feedback on usability and mammography intentions.We enrolled 45 patients and their 21 clinicians. Among those responding in post-visit surveys, 33/37 (89%) patients and 15/16 (94%) clinicians would recommend the guide to others; 33/37 (89%) patients and 15/16 (94%) clinicians felt everything/most things were clear. All other pre-specified acceptability criteria were met. Most patients reported strong intentions for mammography (100% pre-visit, 98% post-visit).Oncology clinicians and older breast cancer survivors found a guide to inform mammography decision-making acceptable and clear. A multisite clinical trial is needed to assess the guide's impact mammography utilization.ClinicalTrials.gov-NCT03865654, posted March 7, 2019.

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 use of growth factors adds considerable expense and some toxicity to adjuvant breast cancer chemotherapy. We tested the feasibility and safety of omitting routine peg-filgrastim use during the paclitaxel portion of the dose-dense doxorubicin-cyclophosphamide–paclitaxel regimen. PATIENTS AND METHODS This was a prospective, single-arm study in which patients 18 to 65 years of age who completed 4 cycles of dose-dense doxorubicin-cyclophosphamide for stage I-III breast cancer received paclitaxel 175 mg/m2 every 2 weeks. Peg-filgrastim was administered after paclitaxel only if patients had had febrile neutropenia in a prior cycle or at investigator discretion if patients had infections or treatment delays of > 1 week. Once a patient received peg-filgrastim, it was administered in all future cycles. The primary end point was the rate of paclitaxel completion within 7 weeks from cycle 1 day 1 to cycle 4 day 1. If ≥ 100 out of 125 patients completed 4 cycles of paclitaxel without dose delay, the regimen would be considered feasible. RESULTS The enrollment goal of 125 patients was met. Median age was 46 years (range, 21-65 years), and 112 patients (90% [95% CI, 83% to 94%]) completed dose-dense paclitaxel within 7 weeks. Omission of peg-filgrastim was not causally related to noncompletion of paclitaxel in any patients. The most common reasons for dose reduction or delays were nonhematologic. One patient experienced febrile neutropenia but was able to complete paclitaxel on time. Eight patients (6.4%) received peg-filgrastim during the trial. Overall, peg-filgrastim was administered in only 4.3% of paclitaxel cycles. CONCLUSION Omission of routine peg-filgrastim during dose-dense paclitaxel according to a prespecified algorithm seems to be safe and feasible and was associated with a 95.7% reduction in the use of peg-filgrastim relative to the current standard of care.

Background: CRA is a surrogate for ovarian toxicity and associated risk of infertility and long-term menopausal symptoms. Therefore, it is important to assess and report the rate of CRA when we study a new neoadjuvant treatment regimen. In the Adjuvant Paclitaxel and Tratuzumab (APT) trial, we found that CRA rate associated with adjuvant TH (12 weeks of paclitaxel and a year of trastuzumab) for human epidermal growth factor receptor-2 (HER2)-positive breast cancer was lower than historically seen with cyclophosphamide-based regimens. The ATEMPT trial allowed a direct comparison of the CRA rate associated with TDM1 and TH. Methods: The ATEMPT trial randomized patients (pts) with Stage I HER2+ breast cancer 3:1 to T-DM1 3.6 mg/kg IV every 3 weeks (w) x17 vs. T 80 mg/m2 IV with H qw x 12 (4 mg/kg load →2 mg/kg), followed by H (6 mg/kg q3w x 13). Participants who reported that they were premenopausal at enrollment were asked to complete menstrual surveys at baseline and every 6-12 months throughout a 36 month follow-up period. For this analysis, CRA was defined as report of no menstruation within the prior six months on a survey completed 18 months after enrollment. Results: Of 512 ATEMPT enrollees, 497 began protocol therapy, 130 (26%) were premenopausal at enrollment and answered baseline menstrual questions, 42 of these 130 were excluded from the current analyses because they did not complete the 18-month survey, and 7 of the remaining 88 had received gonadotropin-releasing hormone agonist before 18 months, leaving 81 for analysis. None had undergone hysterectomy or oophorectomy. Median age was 44 (range 23-53) among the TH patients (n=20), and 46 (range 34-54) among the T-DM1 patients (n=61). On the 18-month survey, 45% of women treated with TH reported at least one one episode of menses during the prior 6 months compared to 75% of women in the T-DM1 arm (p=0.011). Among those ≤ 40 years old, 50% of TH patients and 100% of T-DM1 patients reported menstruation at that timepoint. Please see Table for additional data in subgroups. Conclusions: In this relatively small sample, CRA at 18 months was less common after adjuvant T-DM1 than after TH (though even with TH, nearly half of women did menstruate after chemotherapy, even in the subset aged 41+). This will be reassuring to young patients with HER2-positive breast cancer who seek to maintain ovarian function. Larger studies are needed to confirm this finding and to assess a possible differential impact of these drugs on subgroups based on age, endocrine therapy, and body mass index. Additional research should also focus on menopausal symptoms and actual fertility after receipt of T-DM1. Menstruation in 61 T-DM1 arm patients with informative surveys at 18 monthsMenstruation in 20 TH arm patients with informative surveys at 18 monthsAge at study entry95% CI95% CI≤4012/12 (100%)74-100%4/8 (50%)16-84%41+34/49 (69%)55-82%5/12 (42%)15-72%BMI Citation Format: Kathryn J. Ruddy, Lorenzo Trippa, Jiani Hu, William T. Barry, Chau T. Dang, Denise A. Yardley, Steven J. Isakoff, Vincente V. Valero, Meredith G. Faggen, Therese M. Mulvey, Ron Bose, Douglas J. Weckstein, Antonio C. Wolff, Katherine E. Reeder-Hayes, Hope S. Rugo, Bhuvaneswari Ramaswamy, Dan S. Zuckerman, Lowell L. Hart, Vijayakrishna K. Gadi, Michael Constantine, Kit L. Cheng, Frederick M. Briccetti, Bryan P. Schneider, A. Merrill Garrett, P. Kelly Marcom, Kathy S. Albain, Patricia A. DeFusco, Nadine M. Tung, Blair M. Ardman, Rita Nanda, Rachel C. Jankowitz, Michelle K. DeMeo, Harold J. Burstein, Eric P. Winer, Ian E. Krop, Ann H. Partridge, Sara M. Tolaney. Chemotherapy-related amenorrhea (CRA) after adjuvant trastuzumab emtansine (T-DM1) compared to paclitaxel in combination with trastuzumab (TH) (TBCRC033: ATEMPT trial) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-13-02.

Background: De-escalation of adjuvant therapy following pathologic complete response (pCR) to an abbreviated neoadjuvant regimen in HER2-positive (HER2+) breast cancer is the focus of a recently initiated national trial. However the feasibility of this approach, and its appeal to patients (pts) and providers, has not been formally investigated. Methods: We conducted a single arm pilot trial to determine the feasibility of de-escalated adjuvant therapy (HP-only) in patients with pCR following neoadjuvant THP. Eligible pts had clinical anatomic stage II-III treatment-naïve HER2+ breast cancer. All pts received weekly paclitaxel x12 doses, and HP every 3 weeks x4 doses (up to 6 doses allowed in case of surgical delay). The primary objective was to assess adherence to protocol-specified antibody doublet therapy (HP-only, without cytotoxic chemotherapy) in the adjuvant setting among pts with pCR (ypT0/isN0) following neoadjuvant THP; the primary endpoint was receipt of adjuvant cytotoxic chemotherapy, assessed 3 months post-operatively. Trastuzumab emtansine (T-DM1) was not considered cytotoxic chemotherapy. Among pts with pCR to THP, de-escalation would be deemed infeasible if the true rate of adherence to HP-only were 90% power to reject the null if the true rate of adherence were >95% (Binomial exact test; one-sided alpha=0.05). Questionnaires were administered and records were reviewed to assess pts’ and physicians’ decision-making about adjuvant systemic therapy following pCR and non-pCR. Results: 98 pts received at least one dose of THP on study. Median age was 50 yrs (range 24-78), pts were 99% female, 86% had stage II/14% stage III tumors, 32% ER/PR negative. No pts progressed during neoadjuvant THP. Five pts had incomplete clinical response following THP and received AC prior to surgery. They were classified as non-pCR and censored from further analyses. At the time of analysis, 93 pts were evaluable for response to neoadjuvant therapy (1 pt withdrew from study early; 4 pts had not reached surgery by the data cutoff). Overall pCR rate was 55% (51/93 pts); 10%, 28%, and 2% of pts had RCB I, II, and III responses, respectively (this excluded patients who received AC preoperatively). Of 51 pts who had pCR to THP, 40 had verified data available regarding adjuvant chemotherapy receipt at data cutoff. 39/40 pts (97.5%, 95% CI 86.8-99.9%) who had pCR did not receive adjuvant cytotoxic chemotherapy, meeting the trial’s prespecified threshold for declaring this a feasible approach (primary endpoint), though data remain pending for 11 pts with pCR and will be available at presentation. Of 30 pts who did not experience pCR to THP and had adjuvant chemotherapy status verified at data cutoff, 14/30 pts received adjuvant cytotoxic chemotherapy, and 16/30 pts did not receive adjuvant chemotherapy. The most common reasons cited by pts for non-receipt of adjuvant cytotoxic chemotherapy, despite residual disease at surgery, were (N=21): plan for adjuvant T-DM1 alone (67% of pts), good response to preop chemo (38% of pts), and plan for adjuvant hormonal therapy (24% of pts). The most common reason cited by treating physicians for non-administration of adjuvant chemotherapy, despite residual disease at surgery, was plan for adjuvant T-DM1 (17/21 (81%) physicians). With brief follow-up (median 10.2 mos), there were no breast cancer recurrences. Conclusions: De-escalation of adjuvant cytotoxic chemotherapy among pts who experience pCR in early stage HER2+ breast cancer appears to be an acceptable approach for both pts and physicians, though data are not yet complete and will be updated at the time of presentation. The long-term efficacy of this approach will be determined in the ongoing national CompassHER2-pCR trial. Citation Format: Adrienne G. Waks, Neelam V. Desai, Tianyu Li, Philip D. Poorvu, Ann H. Partridge, Natalie Sinclair, Laura M. Spring, Meredith Faggen, Michael Constantine, Jillian C. Alberti, Julia Deane, Shoshana M. Rosenberg, Sara M. Tolaney, Ian E. Krop, Nadine M. Tung, Nabihah Tayob, Tari A. King, Elizabeth A. Mittendorf, Eric P. Winer. The DAPHNE trial: A feasibility study of chemotherapy de-escalation based on response to neoadjuvant paclitaxel-HP (THP) in HER2-positive breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD3-05.

Chemotherapy-related amenorrhea (CRA) is a surrogate for ovarian toxicity and associated risk of infertility and premature menopause. Here, we compare CRA rate with paclitaxel (T)-trastuzumab (H) to that with ado-trastuzumab emtansine (T-DM1). Patients with T1N0 HER2 + early-stage breast cancer (eBC) enrolled on the ATEMPT trial and were randomized 3:1 to T-DM1 3.6 mg/kg IV every (q) 3 weeks (w) × 17 vs. T 80 mg/m2 with H IV qw × 12 (4 mg/kg load → 2 mg/kg), followed by H (6 mg/kg IV q3w × 13). Enrollees who self-reported as premenopausal were asked to complete menstrual surveys at baseline and every 6–12 months for 60 months. 18-month CRA (no periods reported during prior 6 months on 18-month survey) was the primary endpoint of this analysis. Of 512 ATEMPT enrollees, 123 who began protocol therapy and answered baseline and at least one follow-up menstrual survey were premenopausal at enrollment. 76 had menstrual data available at 18 months without having received a gonadotropin-releasing hormone agonist or undergone hysterectomy and/or oophorectomy. Median age was 45 (range 23–53) among 18 who had received TH and 46 (range 34–54) among 58 who had received T-DM1. The 18-month rate of CRA was 50% after TH and 24% after T-DM1 (p = 0.045). Amenorrhea at 18 months was less likely in recipients of adjuvant T-DM1 than TH. Future studies are needed to understand how T-DM1 impacts risk of infertility and permanent menopause, and to assess amenorrhea rates when T-DM1 is administered after standard HER2-directed chemotherapy regimens.

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: Patient-reported outcomes (PROs) independently and directly describe patient (pt) treatment experiences, complement clinician reports, and are increasingly included in drug development. Eribulin (E) has activity in metastatic breast cancer (MBC) previously treated with > 2 regimens. Limited data are available on the activity of E in earlier lines. This phase II single arm study evaluated the activity, safety, and PROs of E in an earlier line setting for HER2- MBC. Methods: Eligible pts had HER2- MBC, 0-1 prior lines of chemotherapy, and enrolled into one of two parallel cohorts: HR+, TNBC. E was dosed 1.4 mg/m2 weekly, 2 wk on/1 wk off; 1 cycle = 3 wks. The primary objective was overall response rate (ORR); additional objectives included progression-free survival (PFS) and safety. Correlative PRO endpoints included description and comparison of toxicity evaluation by PROs vs provider-report for degree of concordance or divergence for each class of toxicity, and description of QOL over time. Neuropathy was evaluated by the FACT-Neurotoxicity subscale, as well as exploration of predictive host polymorphisms. PRO instruments (PRO-CTCAE, FACT-B and FACT-NTX) were administered electronically at baseline, cycles 1-3, then every other cycle. Results: 83 pts enrolled: 45 HR+ and 38 TNBC. Median age was 56 (range: 34-87). 55.4% were first line, and 66% had received previous taxane in the adjuvant or metastatic setting. ORR for all pts was 25.3% (90% CI: 18%-34%); 35.6% in HR+ (90% CI: 24%-49%) and 13.2% in TNBC (90% CI: 5%-26%). mPFS estimate was 5.8 months (mo) for all pts, HR+ 6.2 mo (90% CI: 5.9-8.7) and TNBC 4.0 mo (90% CI: 3.5-4.8). Related toxicities occurring in > 20% of pts were: fatigue (61.4% overall, 32.5% G1, 27.7% G2, 1.2% G3), alopecia (51.8% overall, 16.9% G1, 32.5% G2), nausea (39.8% overall; 26.5% G1, 12.0% G2, 1.2% G3), peripheral sensory neuropathy (36.1% overall; 18.1% G1, 13.3% G2, 4.8% G3), decreased neutrophil count (32.5% overall; 3.6% G1; 4.8% G2, 13.3% G3, 10.8% G4), peripheral motor neuropathy (22.9% overall, 13.3% G1, 6.0% G2, 3.6% G3), and mucositis (20.5% overall, 16.9% G1, 2.4% G2, 1.2% G3). FACT-B Breast Cancer Concern (BCC) and Trial Outcome Index (TOI) scores were stable during therapy. The greatest mean improvement in summed BCC (mean change 3.3) and TOI (mean change 7.9) compared to baseline occurred at cycle 9 in pts with stable disease. Changes from baseline in the NTX and TOI of FACT-NTX worsened during the first 7 cycles of therapy (mean changes NTX 5.3, TOI 4.8). Pharmacogenomic analysis exploring host polymorphisms and development of neuropathy is ongoing. Conclusions: PROs are indispensable in the evaluation of anti-cancer agents in clinical trials. In this phase II trial, E demonstrated activity and safety in early lines of therapy for HER2- MBC. Additionally, improved QOL metrics were observed among pts experiencing stable disease. CTCAE rates of severe neuropathy were low, however PRO testing by FACT-NTX highlights progressive worsening of neurotoxicity. In contrast to classic CTCAE criteria producing aggregate estimates of toxicity, this phase II trial shows longitudinal collection of PROs provides meaningful, complementary, and dynamic clinical information. Citation Format: Metzger O, Lin NU, Schneider B, Faggen M, Come S, Openshaw T, Constantine M, Walsh J, Giobbie-Hurder A, Burstein HJ, Mayer EL. A phase 2 study of eribulin as early-line treatment for HER2- MBC: Evaluation of efficacy, toxicity, and patient-reported outcomes [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-15-08.

517 Background: Use of growth factors (GF) adds considerable expense and some toxicity to adjuvant breast cancer chemotherapy. We tested the feasibility and safety of omitting routine GF use during the T portion of DD AC-T. Methods: This is a prospective, single-arm study in which patients (pts) who completed 4 cycles of DD-AC proceeded to DD-T 175 mg/m2 every two weeks (wks) without routine GF (NCT02698891). Key inclusion: age≤ 65, ECOG PS≤1, absolute neutrophil count (ANC) ≥1500/mm3, and no febrile neutropenia (FN) during DD-AC. Criteria to treat for T included ANC ≥1000/mm3. Peg-F was given only if pts had FN in a prior cycle, or at investigator discretion if infection or treatment delay > 1 wk. Once Peg-F was given, pts received it in all future cycles. The primary endpoint was the rate of T completion ≤ 7 wks from cycle 1 day 1 (C1D1) to C4D1. Secondary endpoints included total use of Peg-F, rates of hematologic toxicity and FN, reasons for dose modification or hold. If ≥85% of pts completed T on time, the regimen would be considered feasible. If the true on-time completion rate is 75%, the chance the regimen would be declared infeasible is 91%, and if it is 85% the chance that the regimen is falsely declared infeasible is 10% (power = 0.899). ≥100/125 pts had to complete T on time for the regimen to be deemed successful. Results: Among 127 pts enrolled, 125 received ≥1 dose of protocol therapy and are included in the analysis. Median age at registration was 46 (range 21-65). Median C1D1 ANC was 7500/mm3 (range 1500-20500). 112 (90%) (95% CI 83-94%) pts completed DD-T ≤ 7 wks, and 3 (2%) completed within > 7 wks (2 due to neutropenia); 10 (8%) did not complete all cycles of T. Omission of Peg-F was not causally related to non-completion of T in any pts. The most common reasons for dose reduction or delays were non-hematologic. One pt had FN but was able to complete T on time. Eight (6.4%) pts received Peg-F during the trial. Conclusions: Omission of routine GF use during DD-T according to a pre-specified algorithm appears safe, feasible, and was associated with a 95.7% reduction in use of Peg-F, relative to the current standard of care. Additional analyses including cost implications are ongoing. Clinical trial information: NCT02698891.

3506 Background: In prospective observational studies of mCRC patients, higher plasma levels of 25-hydroxyvitamin D have been associated with improved progression-free (PFS) and overall survival (OS), but the role of vitamin D supplementation in the treatment of mCRC is unknown. Methods: SUNSHINE was a multi-center double-blind phase II randomized controlled trial in previously untreated mCRC patients. Patients were eligible if they had histologically confirmed mCRC, no prior therapy for metastatic disease, ECOG PS 0-1, and were not taking vitamin D >2,000 IU/day x 1 year. All subjects received standard treatment with mFOLFOX6 + bevacizumab with 1:1 randomization to concurrent: HiVitD (vitamin D3 po 8,000 IU/d x 2 wks as loading dose followed by 4,000 IU/d) or LowVitD (standard vitamin D3 400 IU/d) until disease progression, intolerable toxicity, or withdrawal of consent. The primary endpoint was PFS, with the sample size designed to provide 80% power to detect a HR of 0.66 for PFS at a 1-sided alpha=0.2. Results: From April 2012 to November 2016, 139 patients were randomized. Median age was 54 yrs (range 24-82), 57% were male, 77% were white, and 7% had received prior adjuvant chemo. Baseline characteristics were balanced between arms except ECOG PS = 0 was 42% vs. 60% in HiVitD vs. LowVitD. Median follow-up was 16.1 mos (range 0-45.9) and median compliance with VitD capsules was 98%. Patients randomized to HiVitD experienced longer PFS than those receiving LowVitD (median PFS, 12.4 vs. 10.7 mos, respectively; log rank P=0.03). After multivariate adjustment for prognostic variables, HR was 0.66 (95% CI, 0.45-0.99, 2-sided P=0.04). Comparing HiVitD vs LowVitD, RR was 58% vs. 63% ( P=0.54) and disease control rate was 100% vs. 94% ( P=0.05). The most common grade 3-4 toxicities were as expected for FOLFOX-bevacizumab, and none were related to vitamin D. Currently, 14 patients are still actively receiving treatment, and OS data are not yet mature. Conclusion: SUNSHINE met its prespecified primary endpoint, with patients randomized to HiVitD experiencing longer PFS compared to those randomized to LowVitD. A larger confirmatory phase III randomized trial appears warranted. Clinical trial information: NCT01516216.