Border Zone Stereotactic Radiosurgery With Bevacizumab in Patients With Glioblastoma Multiforme

Glioblastoma Multiforme (GBM) is the most common primary brain tumor in adults. Unfortunately, despite aggressive surgery, radiation therapy (RT) and chemotherapy, the prognosis for this disease is poor. It is our hypothesis that GBM is a "local" disease wherein treatment failure is due to failure to eradicate tumor cells in the pathways along which the tumor eventually spreads (the "border zone"). The investigators hypothesize that treatment volume escalation will be successful at improving overall survival in patients with GBM when appropriate targeting and precision dose delivery is performed in a single treatment session. The 'border zone' of the tumor will be targeted for SRS (defined as a combination of the MRI volume of gadolinium enhancement plus up to 2 cm of the surrounding T2 volume). This represents the volume of tumor infiltrated white matter and is the route of GBM spread. Bevacizumab, a monoclonal antibody to vascular endothelial growth factor (VEGF), has been used with safety and clinical success with concomitant chemotherapy in solid tumors, including GBM. The investigators further hypothesize that a combined approach of SRS with this VEGF inhibitor will be an effective strategy for GBM because bevacizumab will maximize the effects of radiation in the treated volume and potentially reduce radiation toxicity in the adjacent brain.