PThe phase 3 monarchE trial demonstrates that adjuvant abemaciclib combined with two years of endocrine therapy significantly improves overall survival in high-risk, node-positive HR+/HER2– early breast cancer patients. The 7-year landmark analysis confirmed sustained benefits in invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS).
monarchE enrolled 5,637 patients across two cohorts. Cohort 1 (n=5,120) included patients with ≥4 positive nodes or 1–3 nodes with tumors ≥5 cm or grade 3, while Cohort 2 (n=517) included 1–3 nodes with Ki-67 ≥20%. Patients received abemaciclib 150 mg twice daily plus endocrine therapy or endocrine therapy alone for two years. Earlier analyses showed abemaciclib reduced IDFS events by 25.3% initially and maintained improvements at 5 years (IDFS HR 0.680; DRFS HR 0.675), with absolute 5-year gains of 7.6% for IDFS and 6.7% for DRFS.
The FDA approved adjuvant abemaciclib in October 2021 for Ki-67 ≥20% patients and expanded approval in March 2023 to include all high-risk patients in cohort 1. Lilly Oncology highlighted these results as confirming abemaciclib as standard-of-care for node-positive, high-risk breast cancer, emphasizing timely treatment for eligible patients.
