Inclusion Criteria:

          -  PRIOR TO STEP 1 REGISTRATION

          -  A diagnostic contrast-enhanced magnetic resonance imaging (MRI) (no other scan type
             allowed) of the brain must be performed postoperatively within 72 hours of resection;
             the enhancing tumor must have a maximal diameter of 5 cm; the tumor diameter will be
             the greatest diameter as measured on the contrast-enhanced postoperative MRI and will
             include residual disease and/or the postoperative surgical cavity as appropriate; for
             cases where residual disease or postoperative surgical cavity is NOT identifiable
             (e.g., polar glioblastomas [GBMs] where a polar lobectomy is performed), the patient
             will be excluded from the trial

          -  The GBM tumor must be located in the supratentorial compartment only (any component
             involving the brain stem or cerebellum is not allowed)

          -  Patients must provide study-specific informed consent prior to step 1 registration

          -  PRIOR TO STEP 2 REGISTRATION

          -  Histologically proven diagnosis of glioblastoma (World Health Organization [WHO] grade
             IV) confirmed by central review prior to step 2 registration

          -  Tumor tissue that is determined by central pathology review prior to step 2
             registration to be of sufficient quantity for analysis of
             O6-methylguanin-DNA-methyltransferase (MGMT) status

               -  Patients must have at least 1 block of tumor tissue; submission of 2 blocks is
                  strongly encouraged to maximize the chances of eligibility; at least 1 cubic
                  centimeter of tissue composed primarily of tumor must be present

               -  Diagnosis must be made by surgical excision, either partial or complete;
                  stereotactic biopsy or cavitron ultrasonic suction aspirator (CUSA) technique are
                  not allowed

          -  History/physical examination within 28 days prior to step 2 registration

          -  The patient must have recovered from effects of surgery, postoperative infection, and
             other complications within 28 days prior to step 2 registration

          -  Documentation of steroid doses within 28 days prior to step 2 registration

          -  Karnofsky performance status >= 70 within 28 days prior to step 2 registration

          -  Age >= 18

          -  Absolute neutrophil count (ANC) >= 1,800 cells/mm^3

          -  Platelets >= 100,000 cells/mm^3

          -  Hemoglobin >= 10.0 g/dl (note: the use of transfusion or other intervention to achieve
             hemoglobin (Hgb) >= 10.0 g/dl is acceptable)

          -  Bilirubin =< 1.5 upper limit of normal (ULN)

          -  Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) =< 3 x ULN

          -  Negative serum pregnancy test obtained for females of child-bearing potential within
             28 days prior to step 2 registration

        Exclusion Criteria:

          -  Prior invasive malignancy (except non-melanomatous skin cancer) unless disease-free
             for a minimum of 3 years; (for example, carcinoma in situ of the breast, oral cavity,
             or cervix are all permissible)

          -  Recurrent or multifocal malignant gliomas

          -  Any site of distant disease (for example, drop metastases from the GBM tumor site)

          -  Prior chemotherapy or radiosensitizers for cancers of the head and neck region; note
             that prior chemotherapy for a different cancer is allowable (except temozolomide)

          -  Prior use of Gliadel wafers or any other intratumoral or intracavitary treatment are
             not permitted

          -  Prior radiotherapy to the head or neck (except for T1 glottic cancer), resulting in
             overlap of radiation fields

          -  Severe, active co-morbidity, defined as follows:

               -  Unstable angina at step 2 registration

               -  Transmural myocardial infarction within the last 6 months prior to step 2
                  registration

               -  Evidence of recent myocardial infarction or ischemia by the findings of S-T
                  elevations of >= 2 mm using the analysis of an electrocardiogram (EKG) performed
                  within 28 days prior to step 2 registration

               -  New York Heart Association grade II or greater congestive heart failure requiring
                  hospitalization within 12 months prior to step 2 registration

               -  Serious and inadequately controlled arrhythmia at step 2 registration

               -  Serious or non-healing wound, ulcer or bone fracture or history of abdominal
                  fistula, intra-abdominal abscess requiring major surgical procedure, open biopsy
                  or significant traumatic injury within 28 days prior to step 2 registration, with
                  the exception of the craniotomy for surgical resection

               -  Acute bacterial or fungal infection requiring intravenous antibiotics at the time
                  of step 2 registration

               -  Hepatic insufficiency resulting in clinical jaundice and/or coagulation defects;
                  note, however, that laboratory tests for coagulation parameters are not required
                  for entry into this protocol

               -  Chronic obstructive pulmonary disease exacerbation or other respiratory illness
                  requiring hospitalization or precluding study therapy at the time of step 2
                  registration

               -  Acquired immune deficiency syndrome (AIDS) based upon current Centers for Disease
                  Control and Prevention (CDC) definition; note, however, that human
                  immunodeficiency virus (HIV) testing is not required for entry into this protocol

               -  Any other severe immunocompromised condition

               -  Active connective tissue disorders, such as lupus or scleroderma, that in the
                  opinion of the treating physician may put the patient at high risk for radiation
                  toxicity

               -  End-stage renal disease (ie, on dialysis or dialysis has been recommended)

               -  Any other major medical illnesses or psychiatric treatments that in the
                  investigator's opinion will prevent administration or completion of protocol
                  therapy

          -  Pregnancy or women of childbearing potential and men who are sexually active and not
             willing/able to use medically acceptable forms of contraception

          -  Patents treated on any other therapeutic clinical protocols within 30 days prior to
             step 2 registration

          -  Inability to undergo MRI (e.g., due to safety reasons, such as presence of a
             pacemaker, or severe claustrophobia)

          -  Postoperative tumor plus surgical bed size exceeds 5 cm in maximum diameter.