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

OBJECTIVES: Primary * Determine if dose-intensifying (increasing the "dose-density") the adjuvant temozolomide component of the chemoradiation treatment enhances treatment efficacy as measured by overall survival of patients with newly diagnosed glioblastoma or gliosarcoma. Secondary * Determine if dose-intensifying the adjuvant temozolomide component of the chemoradiation treatment enhances treatment efficacy as measured by progression-free survival. * Determine in patients with unmethylated MGMT (O-6-methylguanine-DNA methyltransferase) if dose-intensifying the adjuvant temozolomide component of the chemoradiation treatment enhances treatment efficacy (overall and progression-free survival) compared with patients receiving conventional temozolomide dosing. * Determine in patients with methylated MGMT if dose-intensifying the adjuvant temozolomide component of the chemoradiation treatment enhances treatment efficacy (overall and progression-free survival) compared with patients receiving conventional temozolomide dosing. * Determine if there is an association between tumor MGMT gene methylation status and treatment response. * Compare and record the toxicities of the conventional and dose-intense chemotherapy regimens. * Evaluate whether 6-month progression-free survival is associated with overall survival. OUTLINE: This is a randomized, multicenter study. Patients are stratified according to recursive partitioning analysis class (III vs IV vs V), MGMT gene methylation status (methylated vs nonmethylated vs indeterminate), and radiotherapy criteria used (standard vs revised European). After completion of study treatment, patients are followed every 3 months for 1 year, every 4 months for 2 years, and then every 6 months thereafter.