High-Dose Esterified Estrogens in Treating Postmenopausal Women With Metastatic Breast Cancer That Has Failed Previous Hormone Therapy

DISEASE CHARACTERISTICS: * Histologically confirmed breast cancer * Metastatic disease * Documented disease progression * Must have received and subsequently failed (due to disease progression) ≥ 2 prior sequential endocrine therapies for treatment of metastatic breast cancer * Disease progression during adjuvant tamoxifen is considered 1 prior therapy * The 2 most recent treatments must have been endocrine agents * At least 1 objective measurable disease parameter * Brain metastases allowed provided both of the following criteria are met: * Brain metastases were previously treated AND are currently stable * Brain metastases are not the only site of metastatic disease * Hormone receptor status * Estrogen and/or progesterone receptor-positive tumor PATIENT CHARACTERISTICS: Age * 18 and over Sex * Female Menopausal status * Postmenopausal, as defined by any of the following: * At least 50 years of age with an intact uterus AND amenorrheic for the past 12 months * At least 50 years of age without a uterus AND follicle-stimulating hormone (FSH) level within postmenopausal range * Under 50 years of age and FSH level within postmenopausal range * Prior bilateral oophorectomy Performance status * ECOG 0-2 Life expectancy * At least 6 months Hematopoietic * Adequate hematologic function Hepatic * Adequate hepatic function * Bilirubin ≤ 1.5 times upper limit of normal * No history of hepatic adenoma Renal * Adequate renal function * No history of hypercalcemia or severe hypocalcemia Cardiovascular * No history of thrombophlebitis or thromboembolic disorders associated with prior estrogen use * No active thrombophlebitis or thromboembolic disorders * No history of uncontrolled hypertension Other * Not pregnant * No undiagnosed abnormal vaginal bleeding * No other serious medical illness * No psychiatric illness that would preclude giving informed consent * No other invasive malignancy within the past 5 years except curatively treated basal cell or squamous cell skin cancer or carcinoma in situ of the cervix PRIOR CONCURRENT THERAPY: Biologic therapy * Not specified Chemotherapy * Prior chemotherapy for metastatic disease allowed * Prior adjuvant chemotherapy allowed Endocrine therapy * See Disease Characteristics Radiotherapy * Prior radiotherapy allowed provided the only site of measurable disease was not irradiated Surgery * Not specified