Real-world efficacy and prognostic factors of CDK4/6 inhibitors in HR+/HER2− metastatic breast cancer: a multicenter retrospective study from the Dongting Lake region of China

Background: CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) have become the standard of care for hormone receptor-positive/human epidermal growth factor receptor 2-negative (HR+/HER2−) metastatic breast cancer (MBC). However, real-world data from China’s central regions remain limited. This study aimed to evaluate the real-world treatment patterns and efficacy of CDK4/6i in HR+/HER2− MBC patients across the Dongting Lake region in China. Methods: This multicenter retrospective study included 590 HR+/HER2− MBC patients treated with CDK4/6i between 2016 and 2025 in five tertiary cancer centers in the Dongting Lake area of Hunan province, China. Patient demographics, treatment patterns, progression-free survival (PFS), and prognostic factors were analyzed. Results: Among 616 initially screened patients, 590 met eligibility criteria. Of these, 63.39% received CDK4/6i as first-line treatment and 25.59% as second-line. The most commonly used CDK4/6i were abemaciclib (33.39%), dalpiciclib (28.98%), palbociclib (25.76%), and ribociclib (10.85%). Median PFS was significantly longer in the first-line group than in the second-line group (32.3 vs. 17.6 months, P