Adjuvant Abemaciclib Plus Endocrine Therapy Yields Improved Outcomes in HR+ ERBB2– High-Risk Early Breast Cancer


Patients with hormone receptor–positive, ERBB2-negative high-risk early breast cancer who received neoadjuvant chemotherapy and adjuvant abemaciclib plus endocrine therapy experienced invasive disease-free survival and distant relapse-free survival benefit vs those with adjuvant endocrine therapy alone.

The addition of abemaciclib (Kisqali) to endocrine therapy resulted in an invasive disease-free survival (iDFS) and distant relapse-free survival (DRFS) benefit compared with endocrine therapy alone in patients with hormone receptor (HR)–positive, ERBB2-negative high-risk early breast cancer treated with chemotherapy vs endocrine therapy alone, according to results from a prespecified analysis of the phase 3 monarchE trial (NCT03155997).1

Findings from the analysis indicated that patient previously treated with chemotherapy experienced a 39% reduction in the risk of iDFS (HR, 0.61; 95% CI, 0.47-0.80; P <.001) and a 39% relative risk reduction in DRFS (HR, 0.61; 95% CI, 0.46-0.81; P <.001) compared with the endocrine therapy–alone arm. This translated to an absolute improvement in the 2-year iDFS rate of 6.6% and an improvement in 2-year DRFS rate of 6.7%. Benefit was observed regardless of pathologic breast tumor size or number of positive nodes at surgery.

Previous findings from the monarchE trial led to the FDA approval of abemaciclib and endocrine therapy in HR-positive, ERBB2-negative, node-positive early breast cancer at high risk of recurrence in patients with a Ki-67 score of 20% or greater.2 As previously reported, this was an open-label, global, randomized trial that assessed the use of abemaciclib and endocrine therapy in the aforementioned population. Patients were eligible for treatment based on lymph node status at surgery or diagnosis. Therefore, lymph node status was only collected at 1 time point and was not available at the time of surgery for the whole population.

In total, 2056 patients (36.5%) enrolled in monarchE received neoadjuvant chemotherapy with most patients receiving an anthracycline- or taxane-based regimen. In total, 2037 of those received at least 1 dose of the study treatment.

An efficacy analysis was not performed among patients who achieve a pathologic complete response (1.6% per arm) or who had no involved axillary lymph nodes at surgery (3.0% vs 2.9%, respectively) due to a limited number of patients. ­­

In the population treated with neoadjuvant chemotherapy and at least 1 dose of the study treatment, safety was consistent with previous findings in the overall population. However, the abemaciclib/endocrine therapy arm had more treatment-emergent adverse effects (AEs), with the most common being diarrhea, infections, neutropenia, and fatigue. Grade 3 or higher AEs included neutropenia and leucopenia. For those who received endocrine therapy alone, the most common grade 3 or higher AEs were arthralgia, hot flashes, and fatigue.


  1. Martin M, Hegg R, Kim SB, et al. Treatment with adjuvant abemaciclib plus endocrine therapy in patients with high-risk early breast cancer who received neoadjuvant chemotherapy. JAMA Oncol. Published online June 2, 2022. doi:10.1001/jamaoncol.2022.1488
  2. FDA approves Verzenio (abemaciclib) as the first and only CDK4/6 inhibitor for certain people with HR+ HER2- high risk early breast cancer. Eli Lilly and Company. News release. October 13, 2021. Accessed June 27, 2022.
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