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.

PURPOSE: CompLEEment-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. METHODS: Eligible 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. RESULTS: In 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. CONCLUSION: The 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).

Full population results from the core phase of CompLEEment-1, a phase 3b study of ribociclib plus letrozole as first-line therapy for advanced breast cancer in an expanded population.

PURPOSE: CompLEEment-1 is a phase 3b trial in an expanded patient population with hormone receptor-positive (HR +), human epidermal growth factor receptor-2-negative (HER2-) advanced breast cancer (ABC), the largest current trial of cyclin-dependent kinase 4 and 6 inhibitors in ABC. METHODS: Patients treated with ≤ 1 line of prior chemotherapy and no prior endocrine therapy for ABC received ribociclib 600 mg/day (3-weeks-on/1-week-off) plus letrozole 2.5 mg/day and additionally monthly goserelin/leuprolide in men and pre-/perimenopausal women. Eligibility criteria allowed inclusion of patients with stable CNS metastases and an Eastern Cooperative Oncology Group performance status of 2. Primary objectives were safety and tolerability, and secondary objectives were efficacy and quality of life (QoL). RESULTS: Overall, 3,246 patients were evaluated (median follow-up 25.4 months). Rates of all-grade and grade ≥ 3 treatment-related adverse events (AEs) were 95.2% and 67.5%, respectively. Treatment-related discontinuations due to all grade and grade ≥ 3 AEs occurred in 12.9% and 7.3% of patients, respectively. Rates of all-grade AEs of special interest (AESI) were as follows: neutropenia (74.5%), increased alanine aminotransferase (16.2%), increased aspartate aminotransferase (14.1%), and QTcF prolongation (6.7%); corresponding values for grade ≥ 3 AESI were 57.2%, 7.7%, 5.7%, and 1.0%, respectively. Median time to progression was 27.1 months (95% confidence interval, 25.7 to not reached). Patient QoL was maintained during treatment. CONCLUSION: Safety and efficacy data in this expanded population were consistent with the MONALEESA-2 and MONALEESA-7 trials and support the use of ribociclib plus letrozole in the first-line setting for patients with HR + , HER2- ABC. TRIAL REGISTRATION: linicalTrials.gov NCT02941926.

Ribociclib plus letrozole in subgroups of special clinical interest with hormone receptor-positive, human epidermal growth factor receptor 2-negative advanced breast cancer: Subgroup analysis of the phase IIIb CompLEEment-1 trial.

BACKGROUND: The phase IIIb CompLEEment-1 study evaluated ribociclib plus letrozole in patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) advanced breast cancer (ABC). Outcomes were investigated in the following subgroups: central nervous system (CNS) metastases, prior chemotherapy for advanced disease, Eastern Cooperative Oncology Group (ECOG) performance status (PS) 2, and visceral metastases plus prior chemotherapy for advanced disease or ECOG PS 2. PATIENTS AND METHODS: Patients with HR+, HER2- ABC without prior hormonal treatment for advanced disease received oral ribociclib (600 mg once daily, 3 weeks on/1 week off) plus letrozole (2.5 mg once daily, continuous). Primary endpoint was safety/tolerability, assessed via occurrence of adverse events (AEs); key secondary endpoints included time to progression (TTP), overall response rate, and clinical benefit rate. RESULTS: 51 patients had CNS metastases, 194 received prior chemotherapy for advanced disease, 112 had ECOG PS 2, 146 had visceral metastases plus prior chemotherapy, and 77 had visceral metastases plus ECOG PS 2. Safety results were consistent with those in the overall CompLEEment-1 population; no new safety concerns were identified. The AE profile was manageable with low rates of discontinuations due to AEs. TTP in patients with CNS metastases was consistent with the overall study population and shorter for other patient subgroups. Each patient subgroup achieved meaningful clinical benefit from treatment, consistent with the overall population. CONCLUSION: These findings confirm the clinical benefit of ribociclib plus endocrine therapy in high-risk patient subgroups of clinical interest commonly underrepresented in clinical trials.