273P Long-term efficacy of adjuvant abemaciclib + endocrine therapy (ET) in key subgroups in the monarchE trial

In monarchE, addition of 2 yrs of adjuvant abemaciclib to ET demonstrated statistically significant and clinically meaningful improvement over ET alone in invasive disease-free survival (IDFS) and overall survival (OS) in patients (pts) with HR+, HER2-, node-positive, high-risk early breast cancer (EBC). The monarchE Cohort 1 (C1) population represents 91% of pts and forms the basis of most global approvals. An updated efficacy analysis (76.8 months median follow-up; data cutoff 15 July 2025) for key subgroups in C1 is presented.