Inclusion Criteria

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