Inclusion Criteria:

• Central pathology confirmed diagnosis of supratentorial grade II oligodendroglioma, astrocytoma, or mixed oligoastrocytoma prior to step 2 registration
• No multifocal disease, based upon the following minimum diagnostic work-up:
  • History/physical examination, including neurologic examination, within 84 days prior to step 2 registration
  • Brain MRI with and without contrast within 84 days prior to Step 2 registration (Note: MRI 70 days after surgery is preferred and highly encouraged)
• The patient must be within one of the following categories:
  • Maximal safe resection with minimal residual disease defined as follows:
    • Removal of T2/fluid-attenuated inversion recovery (FLAIR) abnormalities thought to be primarily tumor, with a residual ≤ 2 cm maximal tumor diameter/T2 FLAIR abnormality on MRI to be done within 84 days post-operatively
    • If there is > 2 cm post-operative residual T2/FLAIR abnormality and the neurosurgeon believes this represents edema and not primarily tumor, the neurosurgeon is encouraged to repeat imaging within the allowed study period (up to 84 days post-operatively) to confirm resolution of edema
      • MRI at the time of enrollment must document a ≤ 2 cm residual maximal tumor diameter/T2 FLAIR abnormality
    • Patients who required a second surgery to obtain a maximal safe resection will be eligible if the second surgery is performed within 84 days of the initial diagnostic procedure
  • Age < 40 (any extent of resection)
  • Age < 50 and preoperative tumor diameter < 4 cm (any extent of resection)
• Karnofsky performance status ≥ 80%
• No prior invasive malignancy (except non-melanomatous skin cancer) unless disease-free for a minimum of 3 years [1,095 days] (For example, carcinoma in situ of the breast, oral cavity, or cervix are all permissible)
• Must be able to undergo MRI of the brain with gadolinium
• No plans for adjuvant radiotherapy or chemotherapy after surgery
• No more than 84 days (12 weeks) since prior surgery
• No brain tumor recurrence
• No prior brain tumor surgery, radiation therapy and/or chemotherapy