The middle to high evidence suggested that PFS was significantly better with CDK4/6 inhibitors in combination with fulvestrant, aromatase inhibitors, or other ET agents than with ET alone for both postmenopausal HR+/HER2− breast cancer and MBC patients, and all with zero heterogeneity, indicating the broad consistency and reliability of multiple investigations. This evidence concerns the gene CYP19A1 and breast carcinoma.