Bevacizumab With or Without Radiation Therapy in Treating Patients With Recurrent Glioblastoma

Inclusion Criteria: * Histopathologically proven diagnosis of glioblastoma or variants (gliosarcoma, giant cell glioblastoma etc); patients will be eligible if the original histology was lower-grade glioma and a subsequent diagnosis of glioblastoma or gliosarcoma is made * Patients who did not have recent surgery for their glioblastoma must have shown unequivocal radiographic evidence for tumor progression by contrast-enhanced magnetic resonance imaging (MRI) scan (or computed tomography \[CT\] scan for patients with non-compatible devices) CT scan within 21 days prior to registration. \* Note: Patients who did have surgery with a post-operative contrast-enhance scan falling outside the 5 week window prior to registration, must have a repeat MRI scan (or CT scan for patients with non-compatible devices) within 21 days prior to registration. * Patients also must have passed an interval of 6 months or greater between completion of prior radiotherapy and registration; if patients have not passed an interval of at least 6 months, they may still be eligible if they meet one or more of the following criteria: * New areas of tumor outside the original radiotherapy fields as determined by the investigator, or * Histologic confirmation of tumor through biopsy or resection, or * Nuclear medicine imaging, magnetic resonance (MR) spectroscopy, or MR perfusion imaging consistent with true progressive disease, rather than radiation necrosis obtained within 28 days of registratio…