Study of Stereotactic Radiosurgery to the Subventricular Zone in Malignant Gliomas

Inclusion Criteria: * Consent to participate in a clinical trial * Confirmed WHO III or WHO IV malignant glioma, based upon Northwell Health neuropathology review. Outside cases must be submitted for central neuropathology review. * Completion of major surgical debulking procedure, defined as residual tumor volume of less than 20% original mass * Age greater than 18 years old. Children are not included because their disease behaves in a biologically distinct manner and there are already national clinical trials specific to them * Patients will not be excluded on the basis of advanced age (i.e., \>75 years old), but there will need to be an intent to deliver standard chemoradiation therapy. Patients scheduled for accelerated radiation therapy are ineligible * Karnofsky performance status of 50 or higher. Patients may require considerable assistance and frequent medical care. * Willingness to sign HIPAA authorization that allows the investigators to continue to obtain clinical information even if patient leaves the study institution for care elsewhere in order to collect long term outcome and toxicity data. * Lobar tumor location (Frontal, temportal, parietal, occipital, or thalamic) Exclusion Criteria: * Inability to consent to participate in a clinical trial, as determined during the standard of care practice evaluation of a malignant brain tumor patient. * Prior malignant glioma treatment less than 12 months prior to chemoradiation therapy, other than surgery with or without Gliadel wafer placement. Patients who received radiation therapy in the treatment of a lower grade malignancy (i.e., low grade glioma now transformed to WHO Grade III or WHO grade IV) are eligible as long as they are eligible for standard chemoradiation therapy and the radiation therapy delivered in the past was more than 12 months prior to planned chemoradiation therapy. * Any localized interstitial radiotherapy treatment * Concurrent clinical trial participation during standard of care therapy. Clinical trial participation is permitted in the event of recurrent disease. * Nonlobar tumor location (e.g., callosal, brainstem, or cerebellar tumors) * Uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements * Any co-morbid systemic illnesses or other severe concurrent disease which, in the judgment of the principal investigator, would make the patient inappropriate for entry into this study or interfere significantly with the proper assessment of safety and toxicity of the proposed regimen * Pregnancy is an exclusion criterion. Pregnant patients will not receive the study treatment. Women of childbearing age are routinely screened prior to radiation therapy administration for pregnancy. If found to be pregnant, then patient will not be offered participation in the trial