Randomized phase 2 trial of endocrine therapy with or without ribociclib for HR+/HER2- mBC after progression on CDK4/6-inhibition

The multicenter randomized phase 2 MAINTAIN trial included patients with HR-positive/HER2-negative metastatic breast cancer whose tumor progressed on previous endocrine therapy (ET, fulvestrant or exemestane) plus CDK4/6-inhibition (palbociclib or ribociclib). Patients switched ET and were randomized to ribociclib or placebo. There was a significant PFS-benefit with switched ET plus ribociclib over switched ET plus placebo: median 5.29 versus 2.76 months (HR 0.57; p=0.006). PFS rate after 12 months was 24.6% versus 7.4%.