Biomarkers and Clinical Features of Metastatic Breast Cancer in Patients Treated With CDK4/6 Inhibitors

This study investigates the clinical course of CDK4/6 inhibitor treated patients in the real-world setting among patients with breast cancer. CDK4/6 inhibitors may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Studying samples of blood, tissue, ascites or pleural effusions, and fresh body fluids or fresh biopsy, from patients with breast cancer that has spread to the other places in the body (metastatic) may help doctors learn more about cancer and the development of drug resistance in patients, and predict how well patients will respond to treatment.