Inclusion Criteria:

- Written informed consent form

- Postmenopausal patients who had had a histologically or cytologically confirmed
breast cancer removed at the time of diagnosis with no evidence of metastases and who
had completed over 5 years of adjuvant therapy with tamoxifen or toremifen before
entering the study

- Age ≥50 years with cessation of menses and Age ＜50 years Postmenopausal status
defined by one of the following:

- FSH level ＞ 30-40 IU/L

- cessation of menses over the past 1 year

- are/become amenorrheic due to either chemotherapy or LHRH, are/become
amenorrheic due to surgical ovarian ablation

- The tumor was to be ER and/or PgR-positive or the receptor status could have been
unknown

- No evidence of recurrence of the disease at entry

- Patient must be accessible for follow-up

Exclusion Criteria:

- Those patients known to have had receptor-negative primary tumors

- Any concurrent malignancy

- Patients who previously received hormone replacement therapy (HRT) during 5 years of
adjuvant therapy with tamoxifen or toremifen

- Patients who are currently receiving other aromatase inhibitors, or chemotherapy

- Patients who have serious cardiovascular or hepatic disease with significantly
abnormal daily function and/or laboratory results

- Life expectancy ＜ 12 months