Study of Tamoxifen and Raloxifene (STAR) for the Prevention of Breast Cancer in Postmenopausal Women

DISEASE CHARACTERISTICS: * Postmenopausal women at increased risk for developing invasive breast cancer, who meet one of the following criteria: * At least 12 months since spontaneous menstrual bleeding * Prior documented hysterectomy and bilateral salpingo-oophorectomy * At least 55 years of age with prior hysterectomy with or without oophorectomy * Age 35 to 54 with a prior hysterectomy without oophorectomy OR with a status of ovaries unknown with documented follicle-stimulating hormone level demonstrating elevation in postmenopausal range * Histologically confirmed lobular carcinoma in situ treated by local excision only OR a minimum projected 5 year probability of invasive breast cancer of at least 1.66%, using Breast Cancer Risk Assessment Profile * No clinical evidence of malignancy on physical exam within the past 180 days * No evidence of suspicious or malignant disease on bilateral mammogram within the past year * No bilateral or unilateral prophylactic mastectomy * No prior invasive breast cancer or intraductal carcinoma in situ * Hormone receptor status: * Not specified PATIENT CHARACTERISTICS: Age: * 35 and over Sex: * Female Menopausal status: * See Disease Characteristics Performance status: * No restricted normal activity for a significant portion of each day Life expectancy: * At least 10 years Hematopoietic: * Granulocyte count at least 1,500/mm\^3 * Complete blood count and differential normal * Platelet count normal Hepatic: * SGOT or SGPT normal * Bilirubin normal * Alkaline phosphatase normal Renal: * Creatinine normal Cardiovascular: * No cerebral vascular accident, transient ischemic attack, atrial fibrillation, or uncontrolled hypertension * No deep vein thrombosis Pulmonary: * No pulmonary embolus Other: * No other prior malignancy within the past 5 years except basal cell or squamous cell skin cancer or carcinoma in situ of the cervix * No concurrent nonmalignant disease that would preclude administration of tamoxifen or raloxifene * No clinical depression, psychiatric condition, or addictive disorder * No uncontrolled diabetes PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * Not specified Endocrine therapy: * At least 3 months since prior estrogen or progesterone replacement therapy, oral contraceptives, androgens, luteinizing hormone-releasing hormone analogs, prolactin inhibitors, or antiandrogens * At least 3 months since prior tamoxifen, raloxifene, or other selective estrogen-receptor modulators of less than 3 months duration * Concurrent Estring allowed Radiotherapy: * No prior breast radiotherapy Surgery: * See Disease Characteristics Other: * No prior systemic adjuvant therapy for breast cancer * No other participation in a cancer prevention or osteoporosis prevention study involving pharmacologic intervention(s) * NSABP-P-1 patients who received placebo are eligible * No concurrent warfarin or cholestyramine * Concurrent calcitonin or nonhormonal medication (e.g., cholecalciferol, fluoride, or bisphosphonates) allowed