Posted: Monday, September 26, 2022
In the primary analysis of the multicenter phase II monarcHER trial, treatment with the CDK4/6 inhibitor abemaciclib plus trastuzumab and fulvestrant significantly improved progression-free survival in patients with hormone receptor–positive, HER2-positive advanced breast cancer compared with trastuzumab plus chemotherapy. Now, the results of the prespecified final analysis, which were presented by Fabrice André, MD, PhD, of Institut Gustave Roussy, Villejuif, France, and colleagues during the European Society for Medical Oncology (ESMO) Congress 2022 (Abstract LBA18), revealed numeric improvements in overall survival and a manageable safety profile for this combination with or without fulvestrant.
A total of 237 patients were randomly assigned in a 1:1:1 ratio to receive abemaciclib plus trastuzumab with (arm A) or without (arm B) fulvestrant or trastuzumab plus standard-of-care chemotherapy (arm C). Exploratory biomarker analyses were conducted, which included RNA sequencing of intrinsic subtypes.
Across the treatment arms, a total of 157 deaths were reported (arm A: 63%; arm B: 68%; arm C: 67%). Follow-up data were provided for a median of 52.9 months. The median duration of overall survival was 30.3 months in arm A, 31.4 months in arm B, and 22.7 months in arm C (arms A vs. C: hazard ratio [HR] = 0.75, P = .243; arms B vs. C: HR = 0.73, P = .177).
Based on the results of the RNA-sequencing analyses, luminal subtypes were associated with longer durations of progression-free (8.6 vs. 5.4 months; HR = 0.54) and overall (31.7 vs. 19.7 months; HR = 0.68) survival than their nonluminal counterparts. The updated progression-free survival and safety findings were found to be consistent with the results of the primary analysis.
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