Palbociclib in Hormone-Receptor–Positive Advanced Breast Cancer

Growth of hormone-receptor-positive breast cancer is dependent on cyclin-dependent kinases 4 and 6 (CDK4 and CDK6), which promote progression from the G1 phase to the S phase of the cell cycle. We assessed the efficacy of palbociclib (an inhibitor of CDK4 and CDK6) and fulvestrant in advanced breast cancer.This phase 3 study involved 521 patients with advanced hormone-receptor-positive, human epidermal growth factor receptor 2-negative breast...