Ribociclib (RIB) + tamoxifen (TAM) or a non-steroidal aromatase inhibitor (NSAI) in premenopausal women with hormone receptor-positive (HR+), HER2-negative (HER2-) advanced breast cancer (ABC) who received prior chemotherapy (CT): MONALEESA-7 subgroup analysis.

1047Background: Although endocrine therapy (ET) and ovarian function suppression is an established first-line treatment for premenopausal patients (pts) with HR+, HER2– ABC, in some cases first-line CT is administered before ET. In the Phase 3 MONALEESA-7 trial (NCT02278120), RIB + TAM/NSAI and goserelin significantly prolonged progression-free survival (PFS) vs placebo (PBO) + TAM/NSAI and goserelin in premenopausal pts with HR+, HER2– ABC. Here, we report results in pts with and without prior CT for ABC. Methods: 672 pts with ≤1 line of prior CT and no prior ET for ABC were randomized 1:1 to RIB (600 mg/day, 3-weeks-on/1-week-off) or PBO + TAM (20 mg/day) or an NSAI (letrozole [2.5 mg/day] or anastrozole [1 mg/day]) and goserelin (3.6 mg every 28 days). The primary endpoint was PFS. Secondary endpoints included overall response rate (ORR) and safety. Prespecified subgroup analyses were performed in pts with and without prior CT for ABC. Results: 47 (14%) pts in each arm had received prior CT for ABC. Th...