Clinical Outcomes After Letrozole Treatment According to the Estrogen Receptor Expression in Postmenopausal Women

Inclusion Criteria: 1. Patients with estrogen receptor(+) and/or progesterone receptor(+) 2. Postmenopausal state was defined the following conditions, at least one of a, b 1. Serum FSH ≥ 30 mIU/mL and Amenorrhea ≥ 1 year for below 55 years, over than 55 years 2. Bilateral oophorectomy 3. Patients have undergone surgery of the breast cancer within 12 weeks and terminated chemotherapy after surgery within 4 weeks. 4. WHO(ECOG) performance status 0-2 5. Adequate haematological function, renal function, hepatic function. 6. No evidence of metastasis. Exclusion Criteria: 1. Metachronous bilateral breast cancer. 2. Metastatic breast cancer (stage IV) 3. Other hormone therapy and Hormonal replacement therapy given within the previous 4 weeks, except for Estring, Vagifem, Estrogen Cream. 4. Patients with Child-Pugh grade C, serum creatinine\>2xUNL 5. Patients with gastrectomy, small bowel resection, malabsorption syndrome and dysphagia.