Safety and Efficacy of Ribociclib in Combination with Letrozole in Patients with HR+, HER2− Advanced Breast Cancer: Results from the Italian Subpopulation of Phase 3b CompLEEment-1 Study

Background Ribociclib plus letrozole demonstrated manageable safety and efficacy profiles in hormone receptor–positive (HR+), human epidermal growth factor receptor-2–negative (HER2−) advanced breast cancer (ABC) in the Phase 3b CompLEEment-1 trial. Objective To evaluate the safety and efficacy of ribociclib plus letrozole in the Italian subpopulation with HR+, HER2− ABC from the CompLEEment-1 trial. Patients and Methods Patients with HR+, HER2− ABC received ribociclib (600 mg/day, 3 weeks on/1 week off) plus letrozole (2.5 mg/day) while men and premenopausal women additionally received goserelin. Patients were allowed with ≤ 1 line of prior chemotherapy and an Eastern Cooperative Oncology Group performance status of ≤ 2. The primary outcome included safety and tolerability. Results Of the 554 Italian patients, 246 (44.4 %) patients completed treatment. The reasons for treatment discontinuation included progressive disease (PD; 36.6 %), adverse events (AEs; 11.9 %), and death (1.6 %). All-grade AEs and grade ≥ 3 AEs occurred in 98.9 % and 77.8 % patients, respectively. The most common treatment-related AEs were neutropenia (73.6 %), followed by leukopenia (32.1 %), and nausea (25.3 %). The overall response rate was 28.2 % (95 % confidence interval [CI], 24.4–32.1); clinical benefit rate was 71.7 % (95 % CI, 67.7–75.4); and median time to progression was 26.7 months (95 % CI, 24.8-non-estimable). Health-related quality of life scores were maintained during treatment. Conclusion The safety and efficacy profiles of ribociclib plus letrozole in the Italian subpopulation was found to be consistent with the CompLEEment-1 global population result, MONALEESA-2, and MONALEESA-7 outcomes, which reaffirm ribociclib plus letrozole as the frontline treatment option in patients with HR+, HER2− ABC. Trial Registration Number and Date of Registration NCT02941926 (30 November 2016).