This study was a multicenter retrospective evaluation of the electronic health records of 212 patients with HR + /HER2− advanced breast cancer in Andalusia, 175 (82.5%) patients using CDK4/6 inhibitors and 37 (17.5%) patients using endocrine therapy without CDK4/6 inhibitors (control group) (Figure S1). This evidence concerns the gene CDK4 and breast cancer.