Systemic therapy relies on targeted drugs for achieving adequate effects: (i) endocrine therapies employing tamoxifen and/or aromatase inhibitors are the schedule for targeted treatment of HR + BC; (ii) a minority also receive chemotherapy; (iii) HER2 + tumors are treated with chemotherapy with HER2-targeted antibodies or small-molecule inhibitor therapy, and (iv) triple-negative tumors receive chemotherapy alone7,8. This evidence concerns the gene CYP19A1 and breast cancer.