DISEASE CHARACTERISTICS:

• Diagnosis of metastatic (stage IV) breast cancer
• Evidence of disease progression
• Measurable disease

• Must have been previously treated with at least 1 hormonal therapy with either an aromatase inhibitor or an estrogen receptor (ER)-modulating drug in the adjuvant or metastatic setting and meets 1 of the following criteria:

  • Hormone-responsive disease:

    • Stable disease (no recurrence or progression for at least 6 months)
    • Objective response

  • Hormone-nonresponsive disease:

    • No stable disease
    • No objective response
• Previously treated CNS disease allowed provided patient has a life expectancy of at least 3 months (phase I patients) (Phase I closed to accrual effective 10/23/2003)
• No CNS metastases (phase II patients)

• Hormone receptor status:

  • ER and/or progesterone receptor positive
• NOTE: As few as 1% positive cells considered positive

PATIENT CHARACTERISTICS:

Age

• 18 and over

Sex

• Female

Menopausal status

• Not specified

Performance status

• Zubrod 0-1

Life expectancy

• See Disease Characteristics

Hematopoietic

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3

Hepatic

• Bilirubin no greater than 2.0 mg/dL (unless evidence of Gilbert's disease)
• SGOT and SGPT less than 3 times upper limit of normal (unless liver involvement by tumor)

Renal

• Creatinine no greater than 1.5 mg/dL

Other

• Not pregnant
• Negative pregnancy test
• Fertile patients must use effective nonhormonal contraception during and for 2 months after study participation
• No medical or psychiatric condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

• Not specified

Chemotherapy

• No more than 2 prior chemotherapy regimens for metastatic disease (phase II patients)

  • No limitations on prior neoadjuvant or adjuvant regimens
• At least 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin)

Endocrine therapy

• See Disease Characteristics
• At least 6 months since prior tamoxifen
• Concurrent stable dose of steroids allowed (phase I patients) (Phase I closed to accrual effective 10/23/2003)

Radiotherapy

• No concurrent radiotherapy

Surgery

• Concurrent surgery allowed provided the need for surgery is not due to disease progression

Other

• Recovered from all prior therapy
• No prior warfarin
• No concurrent cytochrome p450-inducing anti-convulsants
• No other concurrent anticancer therapies
• Concurrent bisphosphonates for bone metastases allowed