- Adding abemaciclib to fulvestrant prolonged survival by 9.4 months in the MONARCH2 phase 3 trial of women with hormone receptor-positive (HR+)/human epidermal growth factor receptor 2 negative (HER2−) advanced breast cancer that advanced on endocrine therapy.
Why this matters
- OS benefit was consistent regardless of menopausal status.
- Benefit was consistent in women with endocrine resistance or primary visceral disease.
- Multicenter double-blind trial of 669 women (median age, 59 years) with advanced disease, randomly assigned 2:1 to receive fulvestrant 500 mg with either abemaciclib or placebo (150 mg, every 12 hours) on a continuous schedule.
- Funding: Eli Lilly and Company.
- Median survival, 47.7 months.
- Abemaciclib+fulvestrant extended survival by 9.4 months (46.7 vs 37.3 months vs fulvestrant alone; HR, 0.757; P=.01).
- Results were even better for those with these stratification factors:
- Primary (vs secondary) resistance to prior endocrine therapy (HR, 0.686; 95% CI, 0.451-1.043).
- Visceral metastasis (HR, 0.675; 95% CI, 0.511-0.891).
- Abemaciclib+fulvestrant was also associated with:
- longer time to disease progression (median, 23.1 vs 20.6 months),
- longer time to chemotherapy (median, 50.2 vs 22.1 months), and
- longer chemotherapy-free survival (median, 25.5 vs 18.2 months).
- No new safety problems emerged.
- Observation time not sufficient for some stratification factors.
- Interim data.