monarchE — Abemaciclib plus Endocrine Therapy as Adjuvant Treatment for High-Risk HR-Positive, HER2-Negative Early Breast Cancer

Phase 3 · 2020 · Breast Cancer

Design

Randomized 1:1 to 2 years of abemaciclib plus standard endocrine therapy vs endocrine therapy alone.

Population

HR-positive, HER2-negative, node-positive high-risk early breast cancer.

Primary Endpoint

invasive disease-free survival (iDFS)

Key Result

5-year analysis (median FU 54 mo): iDFS 83.6% vs 76.0% (HR 0.680, 95% CI 0.599–0.772), a deepening +7.6-point absolute benefit; DRFS HR 0.675 — sustained well beyond the 2-year treatment period.

Guideline Impact

NCCN category 1 for high-risk node-positive HR+/HER2- early breast cancer