Everolimus for postmenopausal women with advanced breast cancer: Updated results of the BOLERO-2 phase III trial.

Abstract

99 Background: Current treatment options for postmenopausal patients with estrogen-receptor–positive breast cancer (BC) who relapse or progress on a nonsteroidal aromatase inhibitor (NSAI) are limited. The BOLERO-2 trial supports the activity of everolimus (EVE; an oral mammalian target of rapamycin [mTOR] inhibitor) added to the steroidal aromatase inhibitor exemestane (EXE) to prolong progression-free survival (PFS) in this patient population. Long-term PFS and survival data are awaited. Methods: BOLERO-2 is a phase 3, double-blind, randomized, international trial comparing EVE (10 mg once daily) + EXE (25 mg once daily) vs. placebo (PBO) + EXE in postmenopausal women with advanced estrogen-receptor–positive BC progressing or recurring after NSAIs (letrozole or anastrozole). Patients were randomized (2:1) to EVE + EXE or PBO + EXE. The primary endpoint was PFS by local investigator assessment. Main secondary endpoints included centrally assessed PFS, overall survival (OS), safety, bone turnover, and overall response rate. Results: Baseline disease characteristics including tumor burden and prior cancer therapy were well balanced between treatment arms (N = 724). Median PFS was doubled and response rates were consistently improved with EVE + EXE (n = 485) vs PBO + EXE (n = 239) in interim analyses. Median PFS by local assessment was ~3 mo with PBO + EXE vs 6.9 mo (hazard ratio [HR], 0.43; P < .0001) and 7.4 mo (HR, 0.44; P < .0001) with EVE + EXE at 7.5 mo and 12.5 mo follow-up, respectively. Fewer deaths were reported with EVE + EXE (17.2%) vs PBO + EXE (22.7%) at 12.5 mo follow-up. Safety profiles were consistent with previous reports for mTOR inhibitors. PFS data including 528 events (protocol-specified final analysis), and updated OS and safety data will be presented. Conclusions: Adding EVE to EXE markedly prolonged PFS in patients with NSAI-refractory advanced estrogen-receptor–positive BC. There were fewer deaths among patients receiving EVE, and further follow-up will evaluate the effect of EVE on OS.