Side effects of CDK4/6 inhibitors in the treatment of HR+/HER2- advanced breast cancer: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND Although combination of cyclin-dependent kinase 4 and 6(CDK4/6) inhibitors with endocrine therapy for advanced breast cancer (ABC) prolongs PFS in patients, but also has associated toxic side effects. However, few previous studies have summarized the toxic and side effects of CDK4/6 inhibitors. Therefore, this study summarized the corresponding toxic and side effects of CDK/6 inhibitors, which is of great importance for doctors and patients to understand how to balance the high survival rate brought by drugs with the decreased quality of life and improve the management of BC. METHODS PubMed, Embase, The Cochrane Library, and VIP databases were systematically searched to collect randomized controlled trials (RCTs) of CDK4/6 inhibitors combined with endocrine therapy for advanced breast cancer from January 2010 to December 2019.Two investigators independently reviewed the literatures. Before using the RevMan 5.3 software for a meta-analysis, date were extracted and the risk of bias with the include studies were assessed. RESULTS A total of 64 RCTs involving 3685 patients were included. Compared with placebo combined with endocrine therapy, CDK4/6 inhibitors combined with endocrine therapy could improve the median progression free survival rate (hazard ratio 0.54, 95% confidence interval (CI):0.50-0.60, P