ER+/PGR+/HER2-negative BC patients mostly receive endocrine therapies such as tamoxifen, letrozole, anastrozole or exemestane; however, cytotoxic chemotherapies such as adriamycin (Doxorubicin), cyclophosphamide, paclitaxel, docetaxel or carboplatin are administered in selected patients. The gene discussed is ESR1; the disease is breast cancer.