As reported in the Journal of Clinical Oncology by Priya Rastogi, MD, and colleagues, an interim analysis of overall survival in the phase III monarchE trial showed no significant benefit with the addition of 2 years of adjuvant abemaciclib to endocrine therapy in patients with hormone receptor–positive, HER2-negative high-risk early breast cancer. The addition of abemaciclib continued to be associated with improved invasive disease–free survival and distant relapse–free survival over longer follow-up.
Priya Rastogi, MD
The trial supported the October 2021 approval of abemaciclib plus endocrine therapy in this setting, as well as the March 2023 expanded indication for the treatment (removing the Ki67 score requirement for high-risk in patient selection).
Study Details and Key Findings
In the trial, patients were randomly assigned to adjuvant endocrine therapy with or without 2 years of abemaciclib. At the preplanned interim analysis of overall survival, death had occurred in 7.4% of patients in the abemaciclib plus endocrine therapy group vs 8.3% of the endocrine therapy group (hazard ratio [HR] = 0.903, 95% confidence interval [CI] = 0.749–1.088, P = .284).
With a median follow-up of 54 months, the benefit of adding abemaciclib was sustained for invasive disease–free survival (HR = 0.680, 95% CI = 0.599–0.772; nominal P < .001) and distant relapse–free survival (HR = 0.675, 95% CI = 0.588–0.774; nominal P < .001). The 5-year absolute improvements in the abemaciclib plus endocrine therapy group were 7.6% and 6.7% for invasive disease–free survival and distant relapse–free survival, respectively, compared with improvements of 6.0% and 5.3% at 4 years and 4.8% and 4.1% at 3 years.
No new safety signals were observed.
The investigators concluded, “Abemaciclib plus endocrine therapy continued to reduce the risk of developing invasive and distant disease recurrence beyond the completion of treatment. The increasing absolute improvement at 5 years is consistent with a carryover effect and further supports the use of abemaciclib in patients with high-risk early breast cancer.”
Dr. Rastogi, of UPMC Hillman Cancer Center and NSABP Foundation, Pittsburgh, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by Eli Lilly and Company. For full disclosures of the study authors, visit ascopubs.org.
