Whole-Brain Radiation Therapy or Stereotactic Radiosurgery With or Without Lapatinib Ditosylate in Treating Patients With Brain Metastasis From HER2-Positive Breast Cancer

This randomized phase II trial studies how well whole-brain radiation therapy or stereotactic radiosurgery with or without lapatinib ditosylate works in treating patients with breast cancer that has too many of a protein called human epidermal growth factor receptor 2 (HER2) on its cells and has spread to the brain. Radiation therapy uses high energy x rays to kill tumor cells and shrink tumors. Stereotactic radiosurgery is a specialized radiation therapy that delivers a single, high dose of radiation directly to the tumor and may kill more tumor cells and cause less damage to normal tissue. Lapatinib ditosylate may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. It is not yet known whether whole-brain radiation therapy or stereotactic radiosurgery together with lapatinib ditosylate is an effective treatment for brain metastasis from breast cancer.