Statistical analysis
CFS
EVENTS
In this exploratory analysis of OS, mOS and OS rates were estimated using the Kaplan–Meier method. The HR for OS was estimated using a Cox proportional hazards model. Patients without events were censored at the date they were last known to be alive. Analyses were performed on the data in the overall trial population, on patients receiving first-line therapy (de novo or late relapse), and on patients receiving second-line therapy (early relapse or one prior ET for ABC). In addition to the OS analyses, in patients receiving first-line therapy, CFS, TTC, and PFS2 were analyzed using the Cox proportional hazards model and Kaplan–Meier method. In the current extended follow-up (data cutoff, January 12, 2022), a sufficient number of events was reported in the first-line ribociclib arm to provide an estimate of mOS. For patients receiving first-line therapy, the rank-preserving structural-failure time model was used as a sensitivity analysis on OS to determine the effects of crossover and administration of subsequent CDK4/6is in the placebo group.