Radiation Therapy to the Head in Preventing Brain Metastases in Women Receiving Trastuzumab and Chemotherapy for Metastatic or Locally Advanced Breast Cancer

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. It is not yet known whether radiation therapy directed at the head is effective in preventing brain metastases in patients with advanced cancer. PURPOSE: This randomized phase III trial is studying radiation therapy to the head to see how well it works in preventing brain metastases in women receiving trastuzumab and chemotherapy for metastatic or locally advanced breast cancer.