Ribociclib plus letrozole in male patients with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer: subgroup analysis of the phase IIIb CompLEEment-1 trial.

purposeCompLEEment-1 (NCT02941926) is a single-arm, open-label, multicentre phase IIIb study investigating the safety and efficacy of ribociclib plus letrozole (RIB + LET) in a large, diverse cohort who have not received prior endocrine therapy (ET) for advanced disease. We present an exploratory analysis of male patients.

methodsEligible patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC), who had no prior ET and ≤ 1 line of prior chemotherapy for advanced disease, received RIB + LET. Male patients also received goserelin or leuprolide. Primary endpoint was safety and tolerability; efficacy was a secondary endpoint.

resultsIn total, 39/3246 patients were male. Baseline characteristics were similar to the overall population. Male patients experienced fewer treatment-related adverse events (AEs) and treatment-related serious AEs compared with the overall population; fewer male patients had treatment-related AEs leading to discontinuation, adjustment/interruption, or additional therapy. One male patient died as a result of a serious AE that was not considered to be treatment-related. The most common AE was neutropenia; the incidence of grade ≥ 3 neutropenia in males (41.0%) was lower than in the overall population (57.2%). Median follow-up was 25.4 months; median time to progression was not reached in males versus 27.1 months for the overall population.

conclusionThe clinical benefit and overall response rates in males were consistent with the overall population. This analysis demonstrates the safety and efficacy of ribociclib in a close-to-real-world setting, supporting the use of RIB + LET in male patients with HR+, HER2- ABC. TRIAL REGISTRATION NUMBER: NCT02941926 (Registered 2016).