328PRibociclib (RIB) plus letrozole (LET) in male patients (pts) with hormone receptor-positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC) from the CompLEEment-1 trial

Abstract Background There is an unmet need to assess efficacy and safety of therapies for ABC in men. The cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitor RIB has been approved for use in combination with LET for the treatment of HR+, HER2– ABC in men and postmenopausal women with no prior therapy for advanced disease. Here we present a subgroup analysis of male pts in CompLEEment-1, an open-label, phase 3b trial evaluating RIB + LET as first-line therapy in a pt population with broad inclusion/exclusion criteria to reflect real-world practice. Methods Pts with HR+, HER2– ABC and no prior hormonal therapy for ABC received RIB (600 mg daily [QD], 3 weeks on/1 week off) + LET (2.5 mg QD, continuous), and concomitant goserelin or leuprolide. Safety and tolerability (primary outcome), overall response rate (ORR), and clinical benefit rate (CBR) were analyzed for male pts in a subgroup analysis. Results There were 39 men in the study. The median follow-up was 10.35 months, and the median duration of exposure to RIB was 8.0 months. Any-grade adverse events (AEs) were reported in 38 pts; 36 AEs were treatment-related. Serious AEs (SAEs) were reported in 4 pts; 1 SAE was related to treatment. No fatal treatment-related SAEs were reported. Most common any-grade AEs (≥ 20%) were neutropenia (n = 14), hot flush (n = 12), diarrhea (n = 10), and fatigue (n = 8). There were 31 pts with at least 1 dose adjustment of RIB; 5 reductions and 27 interruptions were due to AEs. Fourteen pts permanently discontinued treatment: 7 due to progressive disease and 4 due to AEs. ORR in pts with measurable disease was 34.4% (95% confidence interval [CI], 18.6-53.2%), and CBR was 68.8% (95% CI, 50.0-83.9%). Median TTP was not reached. Conclusions This subgroup analysis from CompLEEment-1 supports the safety and efficacy of RIB + LET in men with HR+, HER2– ABC, and adds to the clinical understanding of CDK4/6 inhibitors in men with HR+, HER2– ABC. Clinical trial identification NCT02941926. Editorial acknowledgement Medical editorial assistance was provided by Rob Camp, PhD, of Healthcare Consultancy Group, LLC, and funded by Novartis Pharmaceuticals Corporation. Legal entity responsible for the study Novartis. Funding Novartis Pharmaceuticals. Disclosure M. Campone: Speaker Bureau / Expert testimony: Novartis; Advisory / Consultancy: Lilly. M. De Laurentiis: Honoraria (institution), Advisory / Consultancy: Pfizer; Honoraria (institution), Advisory / Consultancy: Novartis; Honoraria (institution), Advisory / Consultancy: Roche; Honoraria (institution), Advisory / Consultancy: Celgene; Honoraria (institution), Advisory / Consultancy: AstraZeneca. C. Zamagni: Advisory / Consultancy, Research grant / Funding (institution): AstraZeneca; Advisory / Consultancy: Eisai; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Novartis; Advisory / Consultancy, Research grant / Funding (institution): Pfizer; Advisory / Consultancy: PharmaMar; Advisory / Consultancy, Travel / Accommodation / Expenses: Pierre Fabre; Advisory / Consultancy, Research grant / Funding (institution), Travel / Accommodation / Expenses: Roche; Research grant / Funding (institution): Abbvie; Research grant / Funding (institution): Array BioPharma; Research grant / Funding (institution), Travel / Accommodation / Expenses: Celgene; Research grant / Funding (institution): Medivation; Research grant / Funding (institution): Morphotek; Research grant / Funding (institution): Roche/Genentech. M. Agterof: Advisory / Consultancy: Roche. M. Martin: Advisory / Consultancy, Speaker Bureau / Expert testimony: Pfizer; Advisory / Consultancy, Speaker Bureau / Expert testimony: AstraZeneca; Advisory / Consultancy, Speaker Bureau / Expert testimony: Lilly; Advisory / Consultancy: Puma; Advisory / Consultancy: PharmaMar; Advisory / Consultancy, Speaker Bureau / Expert testimony: Novartis; Advisory / Consultancy: Roche-Genentech; Advisory / Consultancy: Taiho Oncology. All other authors have declared no conflicts of interest.