Trastuzumab and Capecitabine in Treating Women With Metastatic Breast Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed breast cancer * Metastatic disease * Patients with only bone metastases are not eligible * Refractory disease, defined as disease progression, drug-related adverse reaction, or disease relapse during or within 12 months after completion of paclitaxel or docetaxel AND doxorubicin or epirubicin administered in the neoadjuvant, adjuvant, or metastatic setting * Total neoadjuvant or adjuvant taxane dose \> 700 mg/m\^2 for paclitaxel or \> 240 mg/m\^2 for docetaxel * Total taxane dose \> 350 mg/m\^2 for paclitaxel or \> 120 mg/m\^2 for docetaxel in the metastatic setting * Total neoadjuvant or adjuvant anthracycline dose \> 240 mg/m\^2 for doxorubicin or epirubicin * Total anthracycline dose \> 120 mg/m\^2 for doxorubicin or epirubicin in the metastatic setting * HER2/neu overexpression * 3+ by immunohistochemistry or positive by fluorescence in situ hybridization * No symptomatic brain metastases * No pleural or pericardial effusion or ascites * Hormone receptor status: * Not specified PATIENT CHARACTERISTICS: Age * 20 to 75 Sex * Female Menopausal status * Not specified Performance status * ECOG 0-2 Life expectancy * At least 3 months Hematopoietic * Absolute neutrophil count ≥ 1,500/mm\^3 * Platelet count ≥ 100,000/mm\^3 * Hemoglobin ≥ 9.0 g/dL Hepatic * SGOT or SGPT ≤ 2.0 times upper limit of normal (ULN) (\< 3.0 times ULN for patients with liver metastases) * Alkaline phosphatase ≤ 2.5 times ULN * Bilirubin ≤ 1.5 mg/dL Renal * Creatinine ≤ 1.2 mg/dL Cardiovascular * LVEF \> 50% Pulmonary * No interstitial pneumonia with pulmonary fibrosis Other * No history of hypersensitivity reactions * No serious, uncontrolled infection * No other malignancy * Not pregnant or nursing PRIOR CONCURRENT THERAPY: Biologic therapy * Prior trastuzumab (Herceptin®) for metastatic disease allowed Chemotherapy * See Disease Characteristics * No prior capecitabine * At least 2 weeks since prior antimetabolites for metastatic disease * At least 4 weeks since prior alkylating agents, carcinostatic antibiotics, or other carcinostatic agents Endocrine therapy * At least 4 weeks since prior goserelin or leuprolide for metastatic disease * At least 2 weeks since prior oral endocrine agents for metastatic disease * No concurrent endocrine therapy Radiotherapy * No prior radiotherapy to target lesions * At least 4 weeks since prior radiotherapy * No concurrent radiotherapy, including radiotherapy for brain metastases Surgery * Not specified Other * Concurrent bisphosphonates for bone metastases allowed