Evolution of resistance in ER+ Breast Cancer

While the combination of endocrine therapy and CDK4/CDK6 inhibitors has been shown to be effective in the metastatic ER+ breast cancer setting, to test whether it is effective in an earlier stage neoadjuvant setting, the FELINE trial (NCT02712723) was established to test the efficacy of letrozole and ribociclib in a ER-positive, HER2-negative patients in a randomized, placebo-controlled, multicenter trial. Patients were randomized to one of three arms: those in Arm A received letrozole and placebo, Arm B letrozole and intermittent ribociclib, and Arm C letrozole and continuous ribociclib. Samples were collected at screening (Day 0), Cycle 1 (Day 14), and end of trial (Day 180). Samples from 24 patients, where cancer cells were present at Day 0 and one additional time point, were... (for more see dbGaP study page.)