A total of 49,223 female breast cancer cases with reported adverse events associated with CDK4/6is were identified, including 4918 cases (10.0 %) for abemaciclib, 38,002 (77.2 %) for palbociclib, and 6303 (12.8 %) for ribociclib (Table 1). This evidence concerns the gene CDK4 and breast cancer.