A prospective randomized phase II trial was conducted to evaluate the time course effects of toremifene (TOR) and letrozole (LET), as adjuvant hormone therapy, on serum lipid profiles and bone metabolism in estrogen receptor (ER)-positive, postmenopausal breast cancer patients.Fifty-four postmenopausal breast cancer patients [ER positive, HER2 negative, T1–2, node metastases (n = 0–3), M0] who had undergone curative resection were enrolled. The gene discussed is ESR1; the disease is breast cancer.