Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed adenocarcinoma of the breast

- Progressive local-regional or metastatic disease

- Unconfirmed new or progressive multiple pulmonary nodules or unequivocal
radiographic evidence of multiple bone metastases allowed

- At least 1 measurable lesion

- At least 20 mm by CT scan or MRI OR at least 10 mm by spiral CT scan

- Nonmeasurable disease includes the following:

- Bone lesions

- Leptomeningeal disease

- Ascites

- Pleural/pericardial effusions

- Lymphangitis cutis/pulmonis

- Inflammatory breast disease

- Abdominal masses not confirmed and followed by imaging techniques

- Cystic lesions

- Disease progression after prior third-generation aromatase inhibitor (e.g.,
anastrozole, exemestane, letrozole, or vorozole)

- Failed no more than 1 prior additive hormonal therapy (e.g., aromatase inhibitor
with or without tamoxifen)

- Disease recurrence identified no more than 12 months since the last prior
adjuvant tamoxifen treatment

- Oophorectomy, ovarian radiotherapy, and luteinizing hormone-releasing
hormone (LH-RH) analogs not considered hormonal therapy regimens

- No brain or leptomeningeal metastases

- No hepatic metastases involving more than one-third of the liver

- No symptomatic pulmonary lymphangitic disease

- Evidence of hormone sensitivity as defined by:

- Relapse after at least 12 months of adjuvant hormonal treatment

- Tumor remission or stabilization before progression for at least 6 months after
prior hormonal therapy for advanced disease

- Postmenopausal as defined by one of the following:

- At least 12 months since last menstrual period

- 4-11 months since last menstrual period and follicle-stimulating hormone (FSH)
in the postmenopausal range

- Prior castration and castrate FSH levels within the postmenopausal range

- Hysterectomy without oophorectomy (FSH in postmenopausal range if age 60 and
under)

- Hormone receptor status:

- Estrogen-receptor and/or progesterone-receptor positive

- At least 10 fmol/mg cytosol protein OR

- Positive by immunohistochemistry

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Sex:

- Female

Menopausal status:

- See Disease Characteristics

- Postmenopausal

Performance status:

- ECOG 0-2

Life expectancy:

- At least 3 months

Hematopoietic:

- WBC at least 2,000/mm^3

- Platelet count at least 100,000/mm^3

- No history of bleeding diathesis

Hepatic:

- See Disease Characteristics

- Bilirubin no greater than 0.8 mg/dL above upper limit of normal (ULN)

- INR no greater than 1.6

- No hepatitis B or C

- No severe hepatic impairment

Renal:

- Calcium no greater than 10% above ULN

- Creatinine no greater than 1 mg/dL above ULN

- No severe renal impairment

Cardiovascular:

- No unstable or uncompensated cardiac condition

Pulmonary:

- No unstable or uncompensated respiratory condition

Other:

- HIV negative

- No AIDS

- No other severe condition or systemic disease that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Prior trastuzumab (Herceptin) allowed

Chemotherapy:

- Prior adjuvant chemotherapy allowed

- No more than 1 prior chemotherapy regimen for metastatic disease

Endocrine therapy:

- See Disease Characteristics

- More than 4 weeks since prior estrogen replacement therapy

- More than 3 months since prior LH-RH analogs

- No other prior additive hormonal therapy except third-generation aromatase inhibitors
or tamoxifen

Radiotherapy:

- See Disease Characteristics

- Concurrent radiotherapy for control of bone pain or other reasons due to established
bone lesions allowed if radiotherapy field is no more than 30% of bone marrow

Surgery:

- See Disease Characteristics

Other:

- More than 4 weeks since prior investigational drug for breast cancer

- No concurrent long-term warfarin

- Concurrent bisphosphonates allowed if dose stable

- Concurrent long-term antiplatelet therapy allowed