Combination Chemotherapy With Trastuzumab in Treating Women With Metastatic Breast Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed metastatic breast cancer c-erbB2 positive (3+ overexpression by the HercepTest™ method) in the primary tumor or metastatic site * At least 1 unidimensionally measurable target lesion * At least 20 mm by conventional techniques OR * At least 10 mm by spiral CT scan * Lesions that have been irradiated in the preceding 3 months cannot be used as target lesions unless they have appeared or clearly progressed since prior irradiation * No bone lesions as the only target lesions * No contralateral breast cancer that is c-erbB2-positive or c-erbB2-negative/unknown, with status determined on a metastatic site * No CNS metastases * CT scan of brain and CSF cytology are required if neurologic symptoms are present * Hormone receptor status: * Any estrogen or progesterone receptor status PATIENT CHARACTERISTICS: Age: * 18 and over Sex: * Female Menopausal status: * Any status Performance status: * ECOG 0-2 Life expectancy: * Not specified 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) * Transaminases less than 2.5 times ULN (5 times ULN if liver metastases present) Renal: * For patients age 18 to 69: * Creatinine no greater than ULN * For patients age 70 and over: * Creatinine clearance normal Cardiovascular: * LVEF normal by MUGA or echocardiogram * No clinical heart failure Pulmonary: * No malignancy-associated dyspnea at rest * No requirement for supportive oxygen therapy Other: * Not pregnant or nursing * No other prior or concurrent malignancy within the past 5 years except adequately treated carcinoma in situ of the cervix or basal cell skin cancer * No psychological, familial, sociological, or geographical condition that would preclude compliance with study therapy and follow-up schedule PRIOR CONCURRENT THERAPY: Biologic therapy: * No prior anti-c-erbB2 antibody, including trastuzumab (Herceptin®) * No other concurrent biologic therapy Chemotherapy: * No more than 1 prior chemotherapy regimen for metastatic breast cancer * Prior combination of cyclophosphamide, methotrexate, and fluorouracil (CMF) allowed in the adjuvant or metastatic setting only if the disease-free interval after completion of CMF was at least 12 months * Prior anthracyclines and/or taxanes allowed * At least 4 weeks since prior anthracyclines * No prior cumulative dose of doxorubicin more than 360 mg/m\^2 * No prior cumulative dose of epirubicin more than 720 mg/m\^2 * No prior cumulative dose of mitoxantrone more than 90 mg/m\^2 * No other concurrent chemotherapy Endocrine therapy: * More than 2 weeks since prior hormonal therapy in the adjuvant or metastatic setting * No concurrent hormonal therapy Radiotherapy: * See Disease Characteristics * No concurrent radiotherapy Surgery: * Not specified Other: * No other concurrent anticancer therapy or investigational drugs * No concurrent bisphosphonates started after study enrollment except for hypercalcemia