Breast Cancer Coverage from Every Angle

Abemaciclib Plus Endocrine Therapy Approved by FDA for Early Breast Cancer

By: JNCCN 360 Staff
Posted: Thursday, October 14, 2021

On October 12, the U.S. Food and Drug Administration (FDA) approved the first CDK4/6 inhibitor, abemaciclib (Verzenio), for adjuvant treatment of breast cancer. Specifically, abemaciclib would be combined with endocrine therapy such as tamoxifen or an aromatase inhibitor for adjuvant treatment of adults with hormone receptor–positive, HER2-negative, node-positive, early breast cancer.

Eligible patients must have early breast cancer at high risk of recurrence and a Ki67 score of at least 20%, as determined by an FDA-approved test. The FDA simultaneously approved the companion diagnostic Ki67 IHC MIB-1 pharmDx assay for selecting eligible patients for this treatment regimen.

The recommended starting dose of abemaciclib is 150 mg taken twice daily in combination with tamoxifen or an aromatase inhibitor until completion of 2 years of treatment, disease recurrence, or unacceptable toxicity. For full prescribing information, visit

The FDA approval was based on results from the open-label multicenter monarchE trial. Researchers recruited adults with hormone receptor–positive, HER2-negative, node-positive, resected, early breast cancer with clinical and pathologic features consistent with a high risk of disease recurrence for the study. Patients were randomly assigned to receive 2 years of abemaciclib plus their physician’s choice of standard endocrine therapy or standard endocrine therapy alone.

A total of 2,003 patients with high risk of recurrence and a Ki67 score of at least 20% had a statistically significant improvement in invasive disease–free survival (P = .0042). After 3 years, invasive disease–free survival was 86.1% for patients administered abemaciclib plus tamoxifen or an aromatase inhibitor and 79.0% for those receiving a tamoxifen or aromatase inhibitor alone. The most common adverse events observed in 20% or more of patients taking abemaciclib with endocrine therapy included diarrhea, infections, neutropenia, fatigue, leukopenia, nausea, anemia, and headache.

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