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