monarchE

NCT03155997 📎

Regimen

Experimental
Abemaciclib 150 mg BID for 2 years plus standard adjuvant endocrine therapy (AI or tamoxifen, with OFS if premenopausal).
Control
Standard adjuvant endocrine therapy alone (AI or tamoxifen, with OFS if premenopausal).

Population

High-risk HR+/HER2- early breast cancer with node-positive disease (>=4 pos nodes, or 1-3 pos nodes plus high-risk features: Ki-67 >=20%, grade 3, or tumor >=5 cm), after definitive locoregional therapy.

Key finding

monarchE established 2-year adjuvant abemaciclib plus endocrine therapy as a new standard for high-risk HR+/HER2- early breast cancer (NCCN v2.2026 category 1). FDA approved October 2021 for node-positive disease with Ki-67 >=20%; label expanded April 2023 to remove the Ki-67 requirement. iDFS benefit deepens with longer follow-up; OS remains a non-significant trend at 5 years.

Source: PMID 32954927

Timeline

  • Publication: 2020 Dec 1

Guideline citations

  • NCCN BREAST