Safety and efficacy of abemaciclib plus endocrine therapy in older patients with hormone receptor-positive/human epidermal growth factor receptor 2-negative advanced breast cancer: an age-specific subgroup analysis of MONARCH 2 and 3 trials

Purpose Abemaciclib in combination with endocrine therapy (ET) has demonstrated significant efficacy benefits in HR+ , HER2− advanced breast cancer patients in the Phase 3 studies MONARCH 2 (fulvestrant as ET) and MONARCH 3 (letrozole or anastrozole as ET). Here, we report age-specific safety and efficacy outcomes. Methods Exploratory analyses of MONARCH 2 and 3 were performed for 3 age groups (