In a prespecified analysis from the phase III monarchE trial reported in JAMA Oncology, Miguel Martín, MD, PhD, and colleagues found that the addition of adjuvant abemaciclib to endocrine therapy was associated with improved outcomes among women with high-risk hormone receptor–positive, HER2-negative, node-positive breast cancer who had received neoadjuvant chemotherapy prior to study enrollment.
The trial showed that the addition of abemaciclib to endocrine therapy significantly improved invasive disease–free survival among all patients.
Miguel Martín, MD, PhD
Study Details
In the open-label trial, 5,637 patients were randomly assigned between July 2017 and August 2019 to receive standard-of-care endocrine therapy for at least 5 years with or without abemaciclib at 150 mg twice daily for 2 years. A total of 2,056 patients (37%) received neoadjuvant chemotherapy prior to enrollment, including 1,025 in the abemaciclib group and 1,031 in the control group; most patients received anthracycline-/taxane-based regimens.
The current analysis evaluated invasive disease–free survival (the primary endpoint of the trial) and distant relapse–free survival in this subgroup through data cutoff in July 2020.
Key Findings
Median follow-up was 19 months (interquartile range = 15.6–23.9 months).
Rates of invasive disease–free survival at 2 years were 87.2% in the abemaciclib group vs 80.6% in the control group (absolute improvement = 6.6%; hazard ratio [HR] = 0.61, 95% confidence interval [CI] = 0.47–0.80). Benefit of abemaciclib was observed among patients with residual tumor size at surgery of ≤ 2 cm (2-year rates = 91.4% vs 82.2%; HR = 0.56, 95% CI = 0.34–0.90) and > 2 cm (85% vs 79%; HR = 0.61, 95% CI = 0.44–0.84) and among patients with one to three positive nodes at surgery (90.8% vs 87.6%; HR = 0.73, 95% CI = 0.43–1.23) and those with four or more positive nodes (85.1 % vs 77.2%; HR = 0.57, 95% CI = 0.41–0.81).
Rates of distant relapse–free survival at 2 years were 89.5% vs 82.8% (absolute improvement = 6.7%; HR = 0.61, 95% CI = 0.46–0.81). Benefit of abemaciclib was observed among patients with residual tumor size at surgery of ≤ 2 cm (2-year rates = 93.7% vs 84.4%; HR = 0.48, 95% CI = 0.28–0.83) and > 2 cm (87.4% vs 81.2%; HR = 0.64, 95% CI = 0.45–0.90) and among patients with one to three positive nodes at surgery (92.1% vs 89%; HR = 0.76, 95% CI = 0.44–1.33) and those with four or more positive nodes (87.7% vs 79.7%; HR = 0.57, 95% CI = 0.39–0.83).
The investigators concluded, “In the randomized clinical trial monarchE, treatment with adjuvant abemaciclib combined with endocrine therapy demonstrated a clinically meaningful improvement in invasive disease–free survival and distant relapse–free survival for patients with [hormone receptor–]positive, HER2-negative, node-positive, high-risk early breast cancer who received neoadjuvant chemotherapy before trial enrollment.”
Dr. Martín, of the Medical Oncology Service, Hospital General Universitario Gregorio Marañon, Universidad Complutense, Centro de Investigación Biomédica en Red-Cáncer, Grupo Español de Investigación en Cáncer de Mama, Madrid, is the corresponding author for the JAMA Oncology article.
Disclosure: The study was funded by Eli Lilly and Company. For full disclosures of the study authors, visit jamanetwork.com.
