KEY TAKEAWAYS
- The monarchE phase III trial aimed to present 5-year efficacy data from a planned interim analysis of OS in high-risk EBC.
- The study demonstrated that combined therapy has better efficacy in preventing disease recurrence and improving OS in high-risk EBC.
For a study, researchers aimed to evaluate 5-year efficacy data from a planned interim analysis of overall survival(OS) in high-risk EBC.
The study randomly assigned patients in a 1:1 ratio to undergo ET for a minimum of 5 years with or without abemaciclib for 2 2-year treatment(tx) period. High-risk EBC was defined as either having at least 4 positive axillary lymph nodes (ALN) or 1-3 ALN with Grade 3 disease and/or a tumor size of at least 5 cm (Cohort 1).
A smaller subset of patients was included with 1-3 positive ALN and central Ki67 of 20% or more (Cohort 2). The intent-to-treat (ITT) population comprised Cohort 1 (5120 patients) and Cohort 2 (517 patients). OS in the ITT population was statistically assessed using the gated strategy, and HR was calculated using the Cox proportional hazard model.
In the ITT population, after a median follow-up of 54 months, abemaciclib demonstrated sustained benefit with an HR of 0.680 (95% CI: 0.599, 0.772) for IDFS and 0.675 (95% CI: 0.588, 0.774) for DRFS. This persistence resulted in a 5-year absolute improvement in IDFS and DRFS rates of 7.6% and 6.7%, respectively, compared to rates of 6.0%/5.3% at 4 years and 4.8%/4.1% at 3 years.
The treatment benefit in Cohort 1 was consistent with the ITT analysis. No new safety signals emerged, and there were fewer deaths in the abemaciclib plus endocrine therapy arm compared to the endocrine therapy arm (208 vs 234; HR 0.903; P=0.284), although significance was not reached.
The study found that abemaciclib plus ET demonstrated sustained efficacy in preventing disease recurrence and improving OS in high-risk EBC patients.
Clinical Trial: https://clinicaltrials.gov/study/NCT03155997
Harbeck N, Rastogi P, O’Shaughnessy J, Boyle F, Cortés J, Rugo HS, Goetz MP, Hamilton EP, Huang C, Senkus-Konefka E, Tryakin A, Neven P, Huober J, Wei RJ, Andre V, Muñoz M, San Antonio B, Shahir A, Martin Jimenez M, Johnston SRD. LBA17 – Adjuvant abemaciclib plus endocrine therapy for HR+, HER2-, high-risk early breast cancer: Results from a preplanned monarchE overall survival interim analysis, including 5-year efficacy outcomes.
