Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed invasive breast cancer of 1 of the following stages:

- Metastatic disease (stage IV)

- Inoperable locally advanced disease

- Disease progression after prior neoadjuvant chemotherapy required

- Disease progression on or after trastuzumab (Herceptin®) based-therapy

- Received 1-3 prior trastuzumab-based regimens

- HER2/neu-positive tumor, defined as 3+ by fluorescent in situ hybridization

- Measurable disease, defined as at least 1 lesion that can be measured in at least one
dimension

- No clinical signs or symptoms of brain and/or leptomeningeal metastases confirmed by
CT scan or MRI

- Brain and/or leptomeningeal metastases allowed if patient has stable lesions
after standard treatment (surgery or radiotherapy), is asymptomatic on
neurological exam, and is not receiving corticosteroid therapy to control
symptoms

- Hormone receptor status:

- Not specified

PATIENT CHARACTERISTICS:

- ECOG performance status 0-1

- Male or female

- Menopausal status not specified

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- Absolute neutrophil count ≥ 1,500/mm^3

- Platelet count ≥ 75,000/mm^3

- Creatinine ≤ 1.5 times upper limit of normal (ULN)

- Bilirubin ≤ 1.5 times ULN

- Alkaline phosphatase < 5 times ULN

- AST and ALT ≤ 2.5 times ULN (5 times ULN if liver metastases are present)

- LVEF above lower limit of normal by echocardiogram or MRI

- No clinical signs or symptoms of heart failure

- No uncontrolled hypertension (i.e., blood pressure ≥ 180/100 mm Hg)

- No significant valvular disease (i.e., aortic or mitral regurgitation of 3 or 4+/4+
severity or stenosis of either valve)

- No history of uncontrolled cardiac arrhythmia

- No symptomatic or asymptomatic myocardial infarction

- No angina pectoris requiring medication

- No other documented significant cardiac event

- No poorly controlled diabetes mellitus (i.e., fasting blood sugar ≥ 200 mg/dL)

- No history of hypersensitivity reaction to trastuzumab

- No AIDS

- No nonmalignant condition requiring ≥ 20 mg of prednisone (or equivalent)

- No other malignancy within the past 5 years except carcinoma in situ of the cervix or
nonmelanoma skin cancer

- No ongoing liver disease, including viral or other hepatitis, alcohol abuse, or
cirrhosis

- No other serious medical illness

- No medical or psychiatric condition that would preclude study participation

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- Recovered from prior therapy

- More than 3 weeks since prior investigational anticancer agents

- More than 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin C),
major surgery, or immunotherapy

- More than 4 weeks since prior radiotherapy except short-course palliative
radiotherapy for bone pain

- More than 2 weeks since prior and no concurrent oral hormonal therapy

- More than 4 weeks since prior fulvestrant

- No prior doxorubicin hydrochloride or doxorubicin HCl liposome at a cumulative dose
of > 360 mg/m^2

- No prior mitoxantrone hydrochloride at a cumulative dose of > 120 mg/m^2

- No prior epirubicin hydrochloride at a cumulative dose of > 600 mg/m^2

- No prior idarubicin at a cumulative dose of > 90 mg/m^2

- No concurrent radiation therapy, including for symptomatic bone metastases