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.