Abemaciclib plus fulvestrant results in a statistically significant survival improvement in patients with hormone receptor (HR)-positive, ERBB2 (formerly HER2)-negative advanced breast cancer (ABC) who progressed after prior endocrine therapy (ET), the latest results from the MONARCH 2 trial suggest. The effect was observed regardless of menopausal status.
The global, randomised, placebo-controlled, double-blind phase 3 trial of abemaciclib plus fulvestrant vs placebo plus fulvestrant enrolled 669 women between August 7, 2014, and December 29, 2015. Analyses for this latest report were conducted at the time of database lock on June 20, 2019.
At the prespecified interim timepoint, 338 deaths (77% of 441 planned for final analysis) were observed in the intention-to-treat population, with median overall survival (OS) of 46.7 months for abemaciclib plus fulvestrant and 37.3 months for placebo plus fulvestrant (hazard ratio [HR] 0.757; 95% CI 0.606-0.945; P=.01).
More pronounced effects were observed in patients with visceral disease (HR 0.675; 95% CI 0.511-0.891) and primary resistance to prior ET (HR 0.686; 95% CI 0.451-1.043). Time to second disease progression (23.1 vs 20.6 months), time to chemotherapy (50.2 vs 22.1 months), and chemotherapy-free survival (25.5 vs 18.2 months) were also significantly improved in the abemaciclib arm vs placebo arm.
No new safety signals were observed for abemaciclib.