Abemaciclib plus endocrine therapy in HR-positive, HER2-negative high-risk early breast cancer: efficacy in nodal subgroups

Abstract

Background In monarchE, 2 years of abemaciclib plus endocrine therapy (ET) significantly reduced the risk of recurrence and mortality in patients with node-positive, high-risk hormone receptor-positive, human epidermal growth factor receptor 2-negative early breast cancer. This analysis provides additional efficacy data based on nodal subgroups. Patients and methods Three nodal subgroups were analyzed in cohort 1, a population comprising 91% of the patients in monarchE: N1 high-risk (1-3 positive nodes with grade 3 tumors and/or tumor size ≥5 cm), N2 [4-9 positive axillary lymph node (ALN)], and N3 (≥10 positive ALN). Median follow-up was 76.8 months. Efficacy outcomes for invasive disease-free survival (IDFS) and distant recurrence-free survival (DRFS) using Kaplan–Meier methods and baseline characteristics are reported for nodal subgroups. Results Kaplan–Meier analyses for IDFS and DRFS highlighted consistent and durable efficacy across nodal subgroups. Within the N1 high-risk group, 68.6% of tumors were grade 3; 57.6% of grade 3 tumors were <5 cm. In ET arm, recurrence risk in the N1 high-risk group was similar to N2. Conclusions The similar recurrence risk for patients in the N1 high-risk and N2 subgroups, and consistent efficacy across nodal subgroups, support addition of 2 years of adjuvant abemaciclib to ET to improve outcomes in patients meeting monarchE cohort 1 N1 high-risk, N2, or N3 criteria.