CDK4 and breast cancer: Based on rich evidence-based medical evidence, authoritative in NCCN Guidelines for Breast Cancer, Version 4.2023 and CSCO Guidelines for the Treatment of Breast Cancer 2023, and other authoritative guidelines, CDK4/6 inhibitors combined with ET are recommended as the first choice for patients with HR+/HER2− advanced breast cancer, so the 4 CDK4/6 inhibitors are all the first choice drugs that are clinically necessary, scoring 5 points.