In terms of specific adverse event analysis, CDK4/6 inhibitors were significantly associated with an increased risk of adverse events, especially in neutropenia (OR = 105.53, 95% CI: 65.24–183.09) and leukopenia (OR = 46.25, 95% CI: 23.20–110.94), which may be related to the high hematological toxicity of palbociclib and ribociclib. Here, CDK4 is linked to neutropenia.