Ribociclib (RIB) + fulvestrant (FUL) for advanced breast cancer (ABC): Progression-free survival (PFS) subgroup and tumor response analyses from MONALEESA-3

Abstract

Background: RIB+FUL prolonged PFS vs placebo (PBO) + FUL in postmenopausal patients (pts) with HR+, HER2‐ ABC in the Phase 3 MONALEESA‐3 study (NCT02422615). Consistent PFS benefit was observed in pts receiving treatment in either the first‐ (1L) or combined second‐line (2L)/early relapse settings. Here we present additional efficacy and pain reduction results from MONALEESA‐3. Methods: Pts who received no or≤1 line of prior endocrine therapy for ABC (i.e. receiving treatment in the 1L or 2L/early relapse settings, respectively) received RIB + FUL (n=484) or PBO +FUL (n=242). Endpoints included, primary: local PFS; secondary: overall response rate and health‐related quality of life (HRQoL). Results: As of Nov 3, 2017, median PFS was prolonged for RIB vs PBO in the separate 2L and early relapse settings (Table). Amongst the full population, 155/379 pts with measurable disease at baseline (41%; 95% CI 35.9‐45.8) in the RIB arm and 52/181 (29%; 95% CI 22.1‐35.3) in the PBO arm had a complete or partial response (P=0.003). The probability of a response by 6 months (RIB vs PBO arm) was 27% (95% CI 22.7‐31.0) vs 16% (95% CI 12.0‐21.6). At Week 8, a decrease from baseline in target lesion(s) size per RECIST was observed in (RIB vs PBO) 232/484 (48%) vs 92/ 242 (38%; P=0.006). A decrease in best%change from baseline in target lesion(s) size per RECIST was reported in 79% of 344 pts in the RIB arm and 66% of 166 pts in the PBO arm. At Cycle 3 Day 1 (Week 8), the absolute mean change from baseline in EORTC QLQ‐C30 pain score was similar in both arms: ‐4.2 RIB (n=361); ‐2.9 PBO (n=169; P=0.517). Conclusions: RIB+ FUL consistently prolonged PFS in the separate 2L and early relapse settings. In the full population, RIB+ FUL demonstrated early tumor size reduction and a higher response rate vs PBO + FUL, consistent with other RIB studies. Pain reduction was similar in both arms, suggesting addition of RIB to FUL does not negatively affect HRQoL.