RATIONALE: Monoclonal antibodies, such as trastuzumab, can block tumor growth in different ways. Some block the ability of tumor cells to grow and spread. Others find tumor cells and help kill them or carry tumor-killing substances to them. Radiation therapy uses high-energy x-rays to kill tumor cells. Trastuzumab may make tumor cells more sensitive to radiation therapy. Giving trastuzumab together with radiation therapy may kill more tumor cells.

PURPOSE: This phase II trial is studying the side effects and how well giving trastuzumab together with external beam radiation therapy works in treating women with stage III or stage IV breast cancer.

OBJECTIVES:

Primary

• Determine the tolerability of trastuzumab (Herceptin®) and concurrent external beam radiotherapy in women with HER2-overexpressing stage III or IV breast cancer.

Secondary

• Determine the pathologic response rate in patients treated with this regimen.
• Determine the locoregional recurrence rate (as site of first recurrence or any recurrence) and time to locoregional recurrence in patients treated with this regimen.
• Determine the time to local progression in patients (who are deemed to be non-surgical candidates) treated with this regimen .

OUTLINE: This is a multicenter study.

Patients receive trastuzumab IV over 30-90 minutes once a week for 5 weeks. Patients also undergo external beam radiotherapy once daily 5 days a week for 5 weeks.

Three weeks after the completion of trastuzumab and radiotherapy, patients undergo surgical evaluation. Patients deemed to be surgical candidates undergo surgery. Patients deemed to be non-surgical candidates continue to receive trastuzumab and external beam radiotherapy for 2 additional weeks.

After completion of study therapy, patients are followed up every 3 months for 2 years and then every 6 months for 3 years.

DISEASE CHARACTERISTICS:

• Histologically confirmed* invasive primary carcinoma of the breast by fine-needle aspiration, core needle biopsy, or incisional biopsy

• Excisional biopsy is not allowed

• Stage III or IV disease (clinical and radiographic staging), including any of the following:

  • Any T with N2 disease (metastasis to ipsilateral axillary lymph nodes fixed to one another or other structures) or N3 disease (metastasis to ipsilateral internal mammary lymph nodes)
  • T4, any N disease
  • Inflammatory disease
  • Supraclavicular and/or infraclavicular adenopathy
  • Distant metastasis with measurable disease in the breast or lymph nodes

• HER2-overexpressing tumor

• Measurable or evaluable disease

• Residual locoregional disease after completion of neoadjuvant chemotherapy OR locoregional recurrent disease

• Synchronous bilateral primary cancers allowed provided the more serious of the two cancers meets staging criteria

• Hormone receptor status not specified

PATIENT CHARACTERISTICS:

• Menopausal status not specified
• WBC > 2,000/mm^3
• Platelet count > 50,000/mm^3
• Hemoglobin > 11 g/dL
• Negative pregnancy test
• Fertile patients must use effective contraception
• Radionucleotide ventriculography/LVEF normal OR ≤ 10% asymptomatic decline from baseline after completion of neoadjuvant chemotherapy

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics
• No prior radiotherapy to the breast or regional lymph nodes
• Concurrent participation in neoadjuvant chemotherapy clinical trials allowed