Medroxyprogesterone Acetate vs Observation for Endometrial Pathology Prevention in Postmenopausal Breast Cancer Patients on Tamoxifen

Study start date: March 1, 1997

DISEASE CHARACTERISTICS: One of the following histologically proven diagnoses: Primary invasive adenocarcinoma of the unilateral or bilateral breast Stage I, IIA, or IIB (T1-3, N0-1, M0) No recurrent invasive breast cancer Ductal carcinoma in situ (DCIS) Lobular carcinoma in situ (LCIS) with microinvasion Paget's disease of the nipple No sarcoma, lymphoma, or apocrine, adenocystic, or squamous cell cancer of the breast Currently free of breast cancer (no evidence of disease) No evidence of distant disease on chest x-ray or chest CT scan and mammogram of the opposite breast within the past year Prior definitive local treatment of primary lesion (mastectomy or breast-sparing procedure with radiotherapy) and either axillary node or sentinel node biopsy Surgical margins clear of both infiltrating carcinoma (any type) and DCIS No gross or microscopically positive margins except: Invasive cancer or DCIS at the focal margin treated with definitive radiotherapy Gross or LCIS at the final margin Biopsy requirement waived for DCIS or LCIS with minimal microinvasion Patients with breast-sparing procedure must have received or be planning to receive radiotherapy at start of tamoxifen treatment No endometrial simple or cystic hyperplasia, proliferative changes, complex (adenomatous) or atypical hyperplasia, or carcinoma Patients must be planning one of the following: Starting adjuvant tamoxifen for five years OR Started tamoxifen within 28 days prior to study and planning to receive adjuvant tamoxifen for five years Hormone receptor status: Candidate for adjuvant tamoxifen therapy PATIENT CHARACTERISTICS: Age: Adult Sex: Female Menopausal status: Postmenopausal defined as: At least 1 year since last menstrual period At least 2 months since bilateral oophorectomy prior to breast cancer diagnosis 4-12 months since last menstrual period and FSH elevated to postmenopausal range Postmenopausal estrogen therapy and 55 years of age or older Performance status: Not specified Life expectancy: Not specified Hematopoietic: Not specified Hepatic: Not specified Renal: Not specified Other: Fertile patients must use effective contraception during and for at least 2 months after study No other malignancy within the past 5 years except adequately treated basal cell or squamous cell skin cancer, carcinoma in situ of the cervix, or stage I or II cancer currently in complete remission No concurrent nonmalignant-related illness that would preclude study PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: Adjuvant chemotherapy allowed No concurrent chemotherapy Endocrine therapy: See Disease Characteristics No prior hormonal treatment for breast cancer (except tamoxifen) No concurrent postmenopausal estrogen therapy Radiotherapy: See Disease Characteristics Surgery: See Disease Characteristics No prior or concurrent hysterectomy Other: No prior or current participation in an adjuvant intergroup trial