Bevacizumab, Temozolomide, and External Beam Radiation Therapy as First-Line Therapy in Treating Patients With Newly Diagnosed Glioblastoma Multiforme or Gliosarcoma

RATIONALE: Monoclonal antibodies, such as bevacizumab, 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. Bevacizumab may also stop the growth of tumor cells by blocking blood flow to the tumor. Drugs used in chemotherapy, such as temozolomide, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Radiation therapy uses high energy x-rays to kill tumor cells. Giving bevacizumab together with temozolomide and radiation therapy may kill more tumor cells. PURPOSE: This phase II trial is studying the side effects and how well giving bevacizumab together with temozolomide and external beam radiation therapy works when given as first-line therapy in treating patients with newly diagnosed glioblastoma multiforme or gliosarcoma.