Capecitabine in Treating Patients With Metastatic Breast Cancer

DISEASE CHARACTERISTICS:

Histologically or cytologically confirmed diagnosis of adenocarcinoma of the breast

Evidence of metastatic involvement (stage IV disease)

Patients must have measurable disease

At least one measurable lesion as defined by the Response Evaluation Criteria in Solid Tumors (RECIST)
Treated brain metastases (surgery or radiation therapy) allowed if clinically stable
Patients with leptomeningeal disease are ineligible

Hormone receptor status:

Not specified

PATIENT CHARACTERISTICS:

Eastern Cooperative Oncology Group (ECOG) performance status 0-2
Male or female
Menopausal status not specified
Absolute neutrophil count (ANC) ≥ 1,500/mm^3
Platelet count ≥ 100,000/mm^3
Creatinine clearance > 50 mL/min
Fertile patients must use effective contraception
No history of another severe and/or life-threatening medical disease
No other active primary malignancy
Not pregnant or nursing
Negative pregnancy test
Patients with asymptomatic HIV infection are eligible
Liver dysfunction score ≤ 9
No pre-existing liver disease (i.e., cirrhosis or active viral hepatitis)
No active gastrointestinal malabsorption illness

No clinically significant cardiac disease, including the following:

Congestive heart failure, symptomatic coronary artery disease, and cardiac arrhythmias not well controlled with medication, or myocardial infarction within the past six months
No prior unanticipated severe reaction to fluoropyrimidine therapy, known hypersensitivity to fluorouracil, or known dihydropyrimidine dehydrogenase deficiency
No history of uncontrolled seizures or central nervous system disorders
No significant history of noncompliance to medical regimens
No clinically significant psychiatric disability that would preclude study compliance

PRIOR CONCURRENT THERAPY:

No previous capecitabine

Up to 3 prior cytotoxic regimens allowed for metastatic disease

Prior noncytotoxic therapy allowed (e.g., hormonal treatment or trastuzumab)
No other concurrent therapies intended to treat the primary condition including chemotherapy, biologic agents, or immunotherapy
No concurrent anti-estrogen therapy, radiation therapy, or investigational systemic therapy
No other concurrent investigational drugs

No concurrent use of the following drugs: warfarin for full anticoagulation, cimetidine, or azidothymidine (AZT)

Mini-dose warfarin for prophylaxis of central venous catheter thrombosis allowed
At least 4 weeks since prior sorivudine or brivudine
Concurrent use of bisphosphonates allowed if initiated before beginning study therapy
Concurrent use of megestrol acetate suspension as an appetite stimulant allowed