Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically and/or cytologically confirmed breast cancer

- Advanced and/or metastatic disease

- At least 1 measurable lesion

- At least 20 mm by conventional techniques OR at least 10 mm by spiral CT scan

- No CNS metastases

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Sex:

- Female

Menopausal status:

- Not specified

Performance status:

- Karnofsky 70-100%

Life expectancy:

- At least 12 weeks

Hematopoietic:

- Neutrophil count at least 1,500/mm^3

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

Hepatic:

- Bilirubin no greater than 1.25 times upper limit of normal (ULN)

- AST/ALT no greater than 2.5 times ULN (5 times ULN if liver metastases present)

- Alkaline phosphatase no greater than 2.5 times ULN (5 times ULN if liver metastases
present OR 10 times ULN if bone metastases present)

- No hepatitis

Renal:

- Creatinine no greater than 1.5 times ULN

- Creatinine clearance at least 50 mL/min

Cardiovascular:

- No clinically significant cardiac disease

- No congestive heart failure

- No symptomatic coronary artery disease

- No cardiac arrhythmias poorly controlled with medication

- No myocardial infarction within the past 12 months even if adequately controlled with
medication

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- HIV negative

- No severe pain inadequately controlled by analgesics

- No prior severe and unexpected reaction to fluoropyrimidine therapy

- No known hypersensitivity to fluorouracil

- No impaired physical integrity of the upper gastrointestinal tract

- No malabsorption syndrome

- No inability to swallow tablets

- No history of uncontrolled seizures, central nervous system disorder, or psychiatric
disability that would preclude study participation

- No serious uncontrolled infection

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- At least 2 but no more than 3 prior chemotherapy regimens

- At least 1 prior chemotherapy regimen containing paclitaxel and an anthracycline as
adjuvant therapy or for advanced and/or metastatic disease

Endocrine therapy:

- Not specified

Radiotherapy:

- No prior radiotherapy to target lesions unless there is evidence of new disease
within the irradiated field

- No concurrent radiotherapy

Surgery:

- No prior organ allografts

Other:

- At least 4 weeks since prior investigational drug

- No concurrent enrollment on other investigational study

- No other concurrent anticancer agents