Radiation Therapy (RT) and Temozolomide (TMZ) in Treating Patients With Newly Diagnosed Glioblastoma or Gliosarcoma

RATIONALE: Radiation therapy uses high-energy x-rays to kill tumor cells. 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. Giving radiation therapy together with temozolomide may kill more tumor cells. It is not yet known which schedule of temozolomide when given together with radiation therapy is more effective in treating glioblastoma or gliosarcoma. PURPOSE: This randomized phase III trial is studying two different schedules of temozolomide to compare how well they work when given together with radiation therapy in treating patients with newly diagnosed glioblastoma or gliosarcoma.