Fulvestrant 250 mg (delivered as a once-monthly 5 ml i.m. injection) has been compared with tamoxifen 20 mg (orally, once daily) in a trial conducted in postmenopausal women with ER-positive and/or PgR-positive or ER/PgR-unknown advanced breast cancer who had not been treated with prior endocrine therapy or chemotherapy for advanced disease. The gene discussed is PGR; the disease is breast carcinoma.