Therefore, ER+ BC is treated with endocrine therapies that inhibit ER signaling, which include aromatase inhibitors (e.g., exemestane), selective ER modulators (SERMs, e.g., tamoxifen) and selective ER degraders (SERDs, e.g., fulvestrant) [3,8,9,10,11]. This evidence concerns the gene CYP19A1 and breast cancer.