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