RATIONALE: Drugs used in chemotherapy, such as capecitabine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing.

PURPOSE: This phase II trial is studying how well capecitabine works in treating patients with metastatic breast cancer.

OBJECTIVES:

Primary

• Determine the response rate in patients with metastatic breast cancer treated with a fixed-dose of capecitabine.

Secondary

• Determine the clinical benefit, time to treatment failure (TTF), safety, and toxicity profile of this regimen in these patients.
• Determine the pharmacokinetics (PK) and pharmacogenetics in these patients.
• Correlate pharmacodynamic effects of this drug with toxicity and response in these patients.
• Determine compliance and adherence to this regimen and correlate with PK parameters in these patients.

OUTLINE: This is an open-label study.

Patients receive a fixed-dose of oral capecitabine twice daily on days 1-14. Courses repeat every 21 days in the absence of disease progression or unacceptable toxicity.

After completion of study treatment, patients are followed periodically.

PROJECTED ACCRUAL: A total of 45 patients will be accrued for this study.

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

Participants were evaluated for adverse events every cycle, or every 3 weeks; median length of time on trial was 7 cycles (or 21 weeks). Potentially treatment-related toxicities of all grades and for all cycles are listed.

The small sample size limited a number of the secondary objectives.