Inclusion Criteria:

          -  Prior to STEP 1 REGISTRATION

          -  Tumor tissue must be available for submission for central pathology review

          -  Documentation from the enrolling site confirming the presence of IDH mutation and
             1p/19q status; the provided information must document assays performed in clinical
             laboratory improvement amendments (CLIA)-approved laboratories

          -  Only English speaking patients are eligible to participate as the cognitive and
             quality of life assessments are available only in English

          -  The patient or a legally authorized representative must provide study-specific
             informed consent prior to study entry

          -  Karnofsky performance status of >= 70 within 30 days prior to registration

          -  Absolute neutrophil count (ANC) >= 1,500 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

          -  BUN < 30 mg/dl

          -  Serum creatinine < 1.5 mg/dl

          -  Post-operative magnetic resonance (MR) imaging with contrast is mandatory obtained for
             radiation therapy planning; enrolling sites are highly encouraged to obtain thin-slice
             (<1.5 mm) 3D T1 pre and post contrast and Axial T2/FLAIR sequences for planning
             purposes

          -  Prior to STEP 2 REGISTRATION

          -  The following baseline neurocognitive assessments must be completed and uploaded prior
             to step 2 registration: HVLT-R, TMT Parts A and B, and COWA

          -  Completion of all items on the following baseline quality of life forms: MDASI-BT,
             LASA QOL, WPAI-GH and Employment Questionnaire. These quality of life forms will be
             required and data entered at step 2 registration.

          -  Financial clearance for proton therapy treatment prior to step 2 registration

          -  Centrally reviewed histologically proven diagnosis of supratentorial, Word Health
             Organization (WHO) grade II or III astrocytoma, oligodendroglioma or oligoastrocytoma,
             with IDH mutation

        Exclusion Criteria:

          -  Definitive clinical or radiologic evidence of metastatic disease; if applicable

          -  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 permissible)

          -  Prior cranial radiotherapy or radiotherapy to the head and neck where potential field
             overlaps would exist

          -  Prior chemotherapy or radiotherapy for any brain tumor

          -  Histologic diagnosis of glioblastoma (WHO grade IV) or pilocytic astrocytoma (WHO
             grade I)

          -  Definitive evidence of multifocal disease

          -  Planned use of cytotoxic chemotherapy during radiation (only adjuvant temozolomide
             therapy will be used on this protocol)

          -  Patients with infra-tentorial tumors are not eligible

          -  Prior history of neurologic or psychiatric disease believed to impact cognitive
             function

          -  The use of memantine during or following radiation is NOT allowed

          -  Severe, active co-morbidity defined as follows:

               -  Unstable angina or congestive heart failure requiring hospitalization within 6
                  months prior to enrollment

               -  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 (Note: EKG to be
                  performed only if clinical suspicion of cardiac issue)

               -  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

               -  Human immunodeficiency virus (HIV) positive with CD4 count < 200
                  cells/microliter; acquired immune deficiency syndrome (AIDS) based upon current
                  Centers for Disease Control and Prevention (CDC) definition; note, however, that
                  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 (i.e., 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

          -  Inability to undergo MRI with and without contrast (e.g. claustrophobia, non-MRI
             compatible implant or foreign body, gadolinium allergy or renal dysfunction preventing
             the patient from receiving gadolinium- institutional guidelines should be used to
             determine if patients are at risk for renal dysfunction); note that patients with
             severe claustrophobia are permitted on this study if they are willing and able to
             undergo MRI with adequate sedation or anesthesia