Capecitabine and Pegylated Interferon Alfa-2a in Treating Patients With Recurrent or Progressive Brain Metastases Due to Breast Cancer

DISEASE CHARACTERISTICS:

* Histologically or cytologically confirmed breast cancer that metastasized to the brain, meeting all of the following criteria:

  * Must have ≥ 1 inoperable brain metastases, meeting 1 of the following criteria:

    * Progressive or recurrent disease after prior whole-brain or stereotactic radiotherapy
    * Ineligible for OR unwilling to be treated with radiotherapy
  * At least 1 unidimensionally measurable brain metastasis by enhanced MRI within the past 21 days
  * No progression or development of central nervous system (CNS) metastasis during prior treatment with capecitabine, fluorouracil, interferon alfa, or interferon beta
* Systemic (i.e., outside the CNS system) cancer must be stable

  * No progressive disease (e.g., liver, lymphangitic, or lung metastases)
* Hormone receptor status:

  * Not specified

PATIENT CHARACTERISTICS:

Age

* 18 and over

Sex

* Male or female

Menopausal status

* Not specified

Performance status

* Karnofsky 70-100%

Life expectancy

* More than 12 weeks

Hematopoietic

* Absolute neutrophil count ≥ 1,500/mm\^3
* Platelet count ≥ 100,000/mm\^3
* Hemoglobin ≥ 10 mg/dL
* No history of idiopathic thrombocytopenic purpura
* No known uncontrolled coagulopathy
* No increased risk for anemia (e.g., thalassemia or spherocytosis)
* No medically problematic anemia

Hepatic

* aspartate aminotransferase (AST or SGOT) and alanine aminotransferase (ALT or SGPT) ≤ 2.5 times upper limit of normal (ULN) (5 times ULN for patients with concurrent liver metastases )
* Bilirubin ≤ 1.5 times ULN
* Alkaline phosphatase ≤ 2.5 times ULN (5 times ULN for patients with concurrent liver metastases; 10 times ULN for patients with concurrent bone metastases)

Renal

* Creatinine ≤ 1.5 times ULN OR
* Creatinine clearance ≥ 30 mL/min

Cardiovascular

* No congestive heart failure
* No symptomatic coronary artery disease
* No medically uncontrolled arrhythmia
* No other clinically significant cardiac disease
* No myocardial infarction within the past 12 months

Gastrointestinal

* No history of inflammatory bowel disease
* Must have intact upper gastrointestinal tract
* Able to swallow tablets
* No malabsorption syndrome
* No history of gastrointestinal bleeding

Immunologic

* No prior unanticipated severe reaction to fluoropyrimidine therapy, interferon, pegylated interferon, or a pegylated moiety
* No known sensitivity to fluorouracil
* No serious uncontrolled infection
* No history of immunologically mediated disease

Other

* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception during and for 6 months after completion of study treatment
* No known dihydropyrimidine dehydrogenase deficiency
* No history of depression characterized by a suicide attempt
* No history of hospitalization for psychiatric disease
* No history of other severe psychiatric disease
* No prior disability as a result of psychiatric disease
* No history of clinically significant psychiatric disability that would preclude study compliance
* No other malignancy within the past 5 years except cured nonmelanoma skin cancer or treated carcinoma in situ of the cervix
* No uncontrolled thyroid dysfunction (e.g., thyroid-stimulating hormone not in normal range)
* No evidence of severe retinopathy (e.g., Cytomegalovirus (CMV) retinitis or macular degeneration)
* No clinically relevant ophthalmologic disorders due to diabetes or hypertension
* No other serious uncontrolled medical conditions that would preclude study participation

PRIOR CONCURRENT THERAPY:

Biologic therapy

* See Disease Characteristics
* At least 3 months since prior interferon alfa or interferon beta

Chemotherapy

* See Disease Characteristics
* At least 3 months since prior capecitabine or fluorouracil

Endocrine therapy

* Concurrent hormonal agents (e.g., tamoxifen, raloxifene, or anastrazole) for breast cancer allowed

Radiotherapy

* See Disease Characteristics

Surgery

* More than 4 weeks since prior major surgery and recovered

Other

* More than 4 weeks since prior participation in another investigational drug study
* At least 4 weeks since prior and no concurrent brivudine or sorivudine
* No concurrent cimetidine
* No other concurrent investigational or commercial agents or therapies for this malignancy