Computer Planned Radiation Therapy Plus Chemotherapy in Treating Patients With Glioblastoma Multiforme

RATIONALE: Radiation therapy uses high-energy x-rays to damage tumor cells. Computer systems that allow doctors to create a 3-dimensional picture of the tumor in order to plan treatment may result in more effective radiation therapy. Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die. Combining radiation therapy with chemotherapy may kill more tumor cells. PURPOSE: Phase I/II trial to study the effectiveness of radiation therapy that has been planned with a computer plus chemotherapy in treating patients who have glioblastoma multiforme.