Abemaciclib plus fulvestrant in East Asian women with HR+, HER2- advanced breast cancer: Overall survival from MONARCH 2.

MONARCH 2 is a global, randomized, double-blind, phase 3 study of abemaciclib/placebo + fulvestrant in patients with hormone receptor positive, human epidermal growth factor receptor 2-negative advanced breast cancer. The East Asian population comprised 212 (31.7%) of the 669 intent-to-treat population in the MONARCH 2 trial. Consistent with the primary analysis, this subpopulation analysis of East Asian patients indicated progression-free survival benefit in the abemaciclib arm. The median overall survival was not reached in the abemaciclib arm and was 48.9 months in the placebo arm (hazard ratio 0.80; 95% confidence interval 0.52-1.24; p = 0.377). In addition, other efficacy endpoints, including time to chemotherapy, chemotherapy free survival, and time to second disease progression, indicated benefit in the abemaciclib arm. This analysis found no new safety concerns with longer follow-up. These findings support the positive benefit-risk balance of the MONARCH 2 regimen in East Asian patients with hormone receptor positive, human epidermal growth factor receptor 2-negative advanced breast cancer.