Ribociclib (RIB) + fulvestrant (FUL) in postmenopausal women with hormone receptor-positive (HR+), HER2-negative (HER2–) advanced breast cancer (ABC): Results from MONALEESA-3.

1000Background: First-line RIB + letrozole significantly prolonged progression-free survival (PFS) in postmenopausal women with HR+, HER2– ABC. Here we report results from MONALEESA-3 (NCT02422615), a Phase 3 randomized, double-blind, placebo-controlled study of RIB + FUL in pts with HR+, HER2− ABC who received no or up to 1 line of prior endocrine therapy (ET) for ABC. Methods: Postmenopausal women with HR+, HER2– ABC were randomized 2:1 (stratified by presence of liver and/or lung metastases and prior ET) to RIB (600 mg/day; 3-weeks-on/1-week-off) + FUL (500 mg) or placebo (PBO) + FUL. Primary objective: investigator-assessed PFS. Secondary objectives included overall survival, overall response rate (ORR), clinical benefit rate (CBR), and safety. Results: 726 pts were enrolled. Baseline pt characteristics were balanced between arms. Median duration from randomization to data cut-off: 20.4 months. The primary objective was met: PFS was significantly improved in the RIB arm vs the PBO arm (hazard ratio: 0...