Clinical Applications of CDK4/6 Inhibitors in HR+/HER2, and Personalized Treatment Strategies: A Narrative Review.

Hormone Receptor-positive/Human Epidermal Growth Factor Receptor 2-negative (HR+/HER2-) breast cancer treatment has made a breakthrough due to the introduction of cyclin-dependent kinases 4 and 6 (CDK4/6) inhibitors. This article mainly reviews the mechanisms of action, clinical efficacy, and current application status of CDK4/6 inhibitors, including Palbociclib, Ribociclib, Abemaciclib, and the emerging Dalpiciclib. The advantages and limitations of different treatment stages are also discussed. CDK4/6 inhibitors have excellent efficacy in prolonging progression-free survival (PFS) and overall survival (OS), and have become a key option for HR+/HER2- breast cancer first-line and adjuvant treatment. The issues of drug resistance and adverse reactions remain severe. Strategies such as combining phosphoinositide 3-kinase (PI3K) inhibitors, immunotherapy, or new estrogen receptor (ER)-degrading agents are being actively explored for drug-resistant patients. The personalized precision therapy may become the core direction for optimizing the application of CDK4/6 inhibitors in the future, which will improve patients' quality of life.