Inclusion Criteria

DISEASE CHARACTERISTICS: Diagnosis of metastatic breast cancer Prior tamoxifen therapy
failure within 1 year of study defined as follows: Prior tamoxifen therapy for metastatic
disease with prior response and progression of disease while still on treatment or within
1 year of last treatment Prior adjuvant tamoxifen therapy for a minimum of 2 years with
subsequent progression of disease while still on treatment or within 1 year of last
treatment Postmenopausal Must be amenorrheic for at least 12 months Removal of both
ovaries or chemotherapy induced menopause allowed At least 1 bideminsionally measurable
lesion No disease restricted only to bone No symptomatic CNS metastases untreated by
surgery or radiotherapy Hormone receptor status: Estrogen or progesterone receptor
positive

PATIENT CHARACTERISTICS: Age: Not specified Menopausal status: Postmenopausal Performance
status: ECOG 0-2 Life expectancy: At least 6 months Hematopoietic: Absolute neutrophil
count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin greater than 9.0
g/dL Hepatic: Bilirubin no greater than 1.5 times upper limit of normal (ULN) AST no
greater than 3 times ULN (no greater than 5 times ULN if liver metastases present) PT and
PTT no greater than 1.25 times ULN Renal: Creatinine no greater than 1.5 times ULN
Cardiovascular: No deep vein thrombosis, retinal vein thrombosis, or stroke within past
year No unstable angina or myocardial infarction within past 6 months Pulmonary: No
pulmonary embolism within past year Other: Not pregnant or nursing No other major illness
or condition that would preclude study

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent trastuzumab (Herceptin)
Chemotherapy: No more than 2 prior chemotherapy regimens, including trastuzumab One
regimen in adjuvant setting and one in metastatic setting OR Two regimens in metastatic
setting No concurrent chemotherapy Endocrine therapy: See Disease Characteristics At least
6 months since prior raloxifene for osteoporosis No prior hormonal, antiestrogen, or
aromatase inhibitors other than tamoxifen for breast cancer At least 4 weeks since prior
tamoxifen No concurrent hormonal replacement therapy, other antiestrogens (including
raloxifene), aromatase inhibitors, or systemic steroids (except physiologic replacement
doses) Radiotherapy: See Disease Characteristics Surgery: See Disease Characteristics
Other: At least 4 weeks since prior investigational drug No concurrent warfarin exept low
dose warfarin for port maintenance No other concurrent investigational agent No concurrent
immunosuppressive therapy