Real-World Study on CDK4/6 Inhibitors Combined With Endocrine Therapy and Subsequent Treatment in HR+/HER2- MBC.

This study is a single-arm, non-interventional study that evaluates the efficacy and safety of the first-line treatment regimen, which includes CDK4/6 inhibitors combined with endocrine therapy. After disease progression on first-line treatment, the second-line systemic treatment regimen (including but not limited to switching to another CDK4/6 inhibitor combined with endocrine therapy, other types of endocrine therapy, chemotherapy, targeted therapy, etc.) will be evaluated.