Exemestane Compared With Tamoxifen in Treating Postmenopausal Women With Breast Cancer

Inclusion criteria

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed early adenocarcinoma of the breast * Completely excised by surgery with curative intent (R0) * Any N OR * Any primary tumor greater than 3 cm OR * Any primary tumor grade III and greater than 1 cm * M0 * No positive supraclavicular nodes * Hormone receptor status: * Estrogen and/or progesterone receptor positive PATIENT CHARACTERISTICS: Age: * Any age * See Menopausal status Sex: * Female Menopausal status: * Postmenopausal * Any age with bilateral oophorectomy or amenorrhea for at least 5 years OR * Age 50 or over: * Natural amenorrhea for at least 1 year OR * Chemotherapy-induced amenorrhea for at least 2 years OR * Radiation-induced amenorrhea (at least 3 months since prior radiotherapy) OR * Under age 50: * If amenorrheic for less than 5 years (any cause) or prior hysterectomy without bilateral surgical oophorectomy, follicle-stimulating hormone must be assayed to confirm postmenopausal status Performance status: * ECOG 0-2 Life expectancy: * Not specified Hematopoietic: * Platelet count greater than 100,000/mm3 * WBC greater than 3,000/mm3 Hepatic: * SGOT or SGPT less than 2.5 times upper limit of normal (ULN) Renal: * Creatinine less than 1.5 times ULN Cardiovascular: * No uncontrolled cardiac disease * No unstable angina * No congestive heart failure or arrhythmia requiring medical therapy * No myocardial infarction within the past 3 months Other: * No severe osteoporosis * No other malignancies within the past 5 years except adequately treated carcinoma in situ of the cervix or basal cell skin cancer * No other serious concurrent disease that would preclude study * No psychiatric disorders that would preclude study PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * No prior neoadjuvant chemotherapy * No more than 10 weeks since completion of prior adjuvant chemotherapy Endocrine therapy: * No prior adjuvant hormonal therapy for breast cancer * No prior neoadjuvant hormonal therapy (prior to surgery) for duration of more than 4 weeks * At least 4 weeks since prior hormone replacement therapy Radiotherapy: * Not specified Surgery: * See Disease Characteristics * No more than 10 weeks since completion of curative surgery Other: * No other concurrent investigational agents or participation in another clinical study (except adjuvant cytotoxic chemotherapy studies) * Concurrent bisphosphonates allowed