A Pilot Study to Evaluate the Immunogenic Effects of Window-of-Opportunity Fractionated Stereotactic Radiotherapy Combined With Atezolizumab for Patients With Newly Diagnosed WHO CNS Grade 4 Glioma (Glioblastoma Multiforme)

Inclusion Criteria: * Diagnosis of glioblastoma multiforme WHO Grade IV * The patient is a surgical candidate, with the surgical intent for a \> 80% resection of the lesion * Negative pregnancy test * ECOG status \<= 2 * Tumor volume \<= 3.5 cm * Adequate organ function * Negative for infectious disease (human immunodeficiency virus, Hepatitis B Virus, Hepatitis C Virus, tubercolosis) Exclusion Criteria: * Patient already underwent surgical total or partial tumor resection, or radiation therapy * Presence of leptomeningeal disease, gliomatosis cerebri, multifocal disease, bilateral cerebral hemisphere involvement ("butterfly" gliomas) * Patients at increased risk of neurologic decompensation * Continued use of high dose intravenous or oral corticosteroids, or \> 8milligrams per day of systemic dexamethasone * Uncontrolled tumor-related pain * Uncontrolled pleural effusion, pericardial effusion, or ascites requiring recurrent drainage procedures (once monthly or more frequently) * Uncontrolled or symptomatic hypercalcemia * History of autoimmune disease or immune deficiency * History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis obliterans), drug-induced pneumonitis, or idiopathic pneumonitis, or evidence of active pneumonitis * Significant cardiovascular disease * History of other malignancy within 1 year prior to screening * Severe infection within 4 weeks prior to initiation of study treatment * History of allogeneic stem cell or organ transplant * Prior treatment with CD137 agonists or immune checkpoint blockade therapies * Treatment with systemic immunostimulatory agents * Treatment with systemic immunosuppressive medication