Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed breast cancer

- Metastatic or recurrent disease

- Considered incurable

- Measurable disease, defined as ≥ 1 unidimensionally measurable lesion ≥ 20 mm by
conventional techniques or ≥ 10 mm by spiral CT scan

- Two primary breast cancers allowed

- Paraffin-embedded primary or metastatic tumor sample available

- No known brain metastases

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Sex

- Male or female

Menopausal status

- Not specified

Performance status

- ECOG 0-2

Life expectancy

- Not specified

Hematopoietic

- Absolute granulocyte count ≥ 1,500/mm^3

- Platelet count ≥ 100,000/mm^3

Hepatic

- Bilirubin ≤ 1.5 times upper limit of normal (ULN)

- AST and ALT ≤ 2.5 times ULN

Renal

- Creatinine ≤ 1.5 times ULN

Other

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No active uncontrolled infection

- No upper gastrointestinal condition or other condition that would preclude ability to
take oral medication

- No other serious medical condition that would preclude study participation

- No psychiatric illness or neurologic disorder that would preclude study compliance

- No other malignancy within the past 5 years except curatively treated nonmelanoma
skin cancer or carcinoma in situ of the cervix or bladder

PRIOR CONCURRENT THERAPY:

Chemotherapy

- At least 4 weeks since prior chemotherapy

- Prior adjuvant chemotherapy allowed

- No more than 1 prior chemotherapy regimen for metastatic or recurrent disease

Endocrine therapy

- At least 5 days since prior hormonal therapy

Radiotherapy

- At least 4 weeks since prior radiotherapy except for low-dose, limited-fraction,
palliative, nonmyelosuppressive radiotherapy, defined as radiotherapy to < 20% of
functioning bone marrow

- If prior radiotherapy was to sole site of disease, must have subsequent documented
disease progression at that site

Surgery

- At least 3 weeks since prior major surgery

Other

- Concurrent prophylactic bisphosphonates allowed, if started prior to study entry

- No concurrent potent inhibitors of cytochrome 3A4, such as erythromycin, diltiazem,
or ketoconazole and similar antifungals

- No other concurrent anticancer therapy

- No other concurrent investigational agents

- No concurrent grapefruit juice