MONARCH 3 — A Study of Abemaciclib (LY2835219) in Combination With a Nonsteroidal Aromatase Inhibitor in Postmenopausal Women With Breast Cancer (MONARCH 3)

Phase 3 · 2017 · Breast Cancer

Design

Randomized double-blind trial of abemaciclib plus a nonsteroidal aromatase inhibitor (anastrozole or letrozole) versus placebo plus AI as initial therapy.

Population

Postmenopausal women with HR-positive, HER2-negative advanced breast cancer with no prior systemic therapy for advanced disease.

Primary Endpoint

progression-free survival (PFS)

Key Result

PFS 28.2 vs 14.8 months (HR 0.54); final overall survival numerically longer (66.8 vs 53.7 months) but not statistically significant.

Guideline Impact

NCCN category 1 first-line CDK4/6 inhibitor plus aromatase inhibitor for HR+/HER2- metastatic breast cancer