Overall Survival with Ribociclib plus Fulvestrant in Advanced Breast Cancer

Abstract

BACKGROUND In an earlier analysis of this phase 3 trial, ribociclib plus fulvestrant showed a greater benefit with regard to progression-free survival than fulvestrant alone in postmenopausal patients with hormone-receptor positive, human epidermal growth factor receptor 2 (HER2) negative advanced breast cancer. Here we report the results of a protocol-specified second interim analysis of overall survival. METHODS Patients were randomly assigned in a 2;1 ratio to receive either ribociclib or placebo in addition to fulvestrant as first-line or second-line treatment. Survival was evaluated by means of a stratified log-rank test and summarized with the use of Kaplan Meier methods. RES U ITS This analysis was based on 275 deaths: 167 among 484 patients (34.5%) receiving ribociclib and 108 among 242 (44.6 /o) receiving placebo. Ribociclib plus fulvestrant showed a significant overall survival benefit over placebo plus fulvestrant. The estimated overall survival at 42 months was 57.8% (95% confidence interval [CI], 52.0 to 63.2) in the ribociclib group and 45.9% (95% CI, 36.9 to 54.5) in the placebo group, for a 28 /0 difference in the relative risk of death (hazard ratio, 0.72; 95% Cl, 0.57 to 0.92; P=0.00455). The benefit was consistent across most subgroups. In a descriptive update, median progression-free survival among patients receiving first-line treatment was 33.6 months (95% CI, 27.1 to 41.3) in the ribociclib group and 19.2 months (95% Cl, 14.9 to 23.6) in the placebo group. No new safety signals were observed. CONCLUSIONS Ribociclib plus fulvestrant showed a significant overall survival benefit over placebo plus fulvestrant in patients with hormone-receptor positive, HER2-negative advanced breast cancer. (Funded by Novartis; MONALEESA-3 ClinicalTrials.gov number, NCT02422615.)