After a CDK4/6 Inhibitor: State of the Art in Hormone Receptor-Positive Metastatic Breast Cancer.

CDK 4/6 inhibitors (CDK4/6i) remain part of the standard first-line treatment for patients with hormone receptor-positive metastatic breast cancer, offering demonstrable improvements in both progression-free survival and overall survival. However, resistance inevitably develops, and the optimal treatment sequencing after CDK4/6i progression remains undefined. Tumor heterogeneity and diverse resistance mechanisms-including alterations in and -complicate treatment decisions in the post-CDK4/6i setting.