Study details
The monarchE trial involved patients with HR+, HER2–, high-risk early breast cancer who had undergone surgery and, as indicated, radiotherapy and/or adjuvant/neoadjuvant chemotherapy. Patients with four or more positive nodes or one to three nodes and either tumors of size ≥5 cm, histologic grade 3, or central Ki-67 ≥20% were eligible; 5,637 patients were randomly assigned in a 1:1 ratio to receive standard-of-care adjuvant endocrine therapy (ET) with or without abemaciclib (150 mg twice daily for 2 years).
A preplanned interim analysis was carried out after 323 IDFS events were observed in the intent-to-treat population. The results, as published last year in the Journal of Clinical Oncology, show that abemaciclib plus ET yielded superior IDFS in comparison with ET alone (P = .01; hazard ratio, 0.75; 95% confidence interval, 0.60-0.93), with 2-year IDFS rates of 92.2% vs. 88.7%.
In the press release announcing the approval of the new indication, the manufacturer notes that the approval was based on the results from a subgroup of 2,003 patients whose tumors had a Ki-67 score of ≥20% and who were also at high risk for recurrence (≥four positive axillary lymph nodes [ALN], or one-three positive ALN with grade 3 disease and/or tumor size ≥5 cm).
There was a statistically significant improvement in IDFS for this prespecified subgroup of patients (HR, 0.643; 95% CI, 0.475-0.872; P = .0042).
With additional follow-up, conducted post hoc, the results showed a 37% decrease in the risk for breast cancer recurrence or death, compared with ET alone (HR, 0.626; 95% CI, 0.49-0.80) and an absolute benefit in IDFS event rate of 7.1% at 3 years. IDFS was 86.1% for abemaciclib plus ET vs. 79.0% for ET alone.
Adverse reactions from monarchE were consistent with the known safety profile for abemaciclib, the company noted. Safety and tolerability were evaluated in 5,591 patients. The most common adverse reactions reported (≥10%) with abemaciclib plus ET vs. ET alone were diarrhea (84% vs. 9%), infections (51% vs. 39%), neutropenia (46% vs. 6%), fatigue (41% vs. 18%), leukopenia (38% vs. 7%), nausea (30% vs. 9%), anemia (24% vs. 4%), headache (20% vs. 15%), vomiting (18% vs. 4.6%), stomatitis (14% vs. 5%), lymphopenia (14% vs. 3%), thrombocytopenia (13% vs. 2%), decreased appetite (12% vs. 2.4%), increased ALT (12% vs. 6%), increased AST (12% vs. 5%), dizziness (11% vs. 7%), rash (11% vs. 4.5%), and alopecia (11% vs. 2.7 %).
A version of this article first appeared on Medscape.com.