Abstract: Objective To systematically evaluate the efficacy and safety of cyclin dependent kinase (CDK) 4/6 inhibitors combined with nonsteroidal aromatase inhibitors for advanced breast cancer. 
Methods Pubmed, The Cochrane Library, EMbase, CNKI, WanFang Data, and VIP databases were electronically searched to collect relevant literature of CDK4/6 inhibitors combined with nonsteroidal aromatase inhibitors for advanced breast cancer from inception to February 1st, 2023. After back-to-back screening of the literature, data extraction, and evaluation of the risk of bias in the included studies, meta-analysis was performed using Rev Man 5.3 software. 
Results There were 8 articles included in the meta-analysis, with a total of 2 706 patients. Meta-analysis results showed that compared with placebo combined with nonsteroidal aromatase inhibitor, CDK4/6 inhibitor combined with nonsteroidal aromatase inhibitor could prolong progression-free survival (PFS) of patients with advanced breast cancer (RR=0.58, 95%CI: 0.51-0.64, P＜0.001), improve objective response rate (ORR) (RR=1.34, 95%CI: 1.20-1.48, P＜0.001) and clinical benefit rate (RR=1.11, 95%CI: 1.06-1.16, P＜0.001). In terms of safety, the incidence of grade 3-4 adverse reactions in patients treated with CDK4/6 inhibitors combined with nonsteroidal aromatase inhibitors was higher (RR=2.63, 95%CI: 2.17-3.19, P＜0.001). Among them, the incidence of adverse reactions such as leukopenia, neutropenia, anemia, fatigue, vomiting, and diarrhea in the experimental group was higher than that in the control group (P＜0.05). There was no significant difference in the incidence of constipation and headache between the two groups (P＞0.05). 
Conclusion CDK4/6 inhibitors combined with nonsteroidal aromatase inhibitors for the patients with advanced breast cancer could prolong PFS, improve ORR and clinical benefit rate, while increasing the incidence of grade 3 to 4 adverse reactions. 

Key words: breast neoplasms, CDK4/6 inhibitor, nonsteroidal aromatase inhibitors