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Bevacizumab (Avastin®; Genentech, South San Francisco, CA) is a monoclonal antibody that targets the vascular endothelial growth factor (VEGF), a predominant ligand for the VEGF receptors (VEGFRs) Flt-1 and KDR.1 The binding of VEGF to its receptors promotes endothelial cell proliferation as well as angiogenesis — a process required for tumor growth beyond 0.125 mm that involves the formation of new blood vessels from existing vasculature. The rationale for targeting angiogenesis in brain tumors is based on the highly vascularized nature of malignant gliomas and the increased expression of angiogenic mediators, including VEGF, within brain tumors relative to nonmalignant tissue.2-5 Several mechanisms of action have been proposed for antiangiogenic therapies, including the inhibition of tumor-associated neoangiogenesis, a direct effect on VEGFR-expressing tumor cells, potential injury to glioma stem cells by disruption of the microvascular stem cell niche, and the normalization of the tumor-associated vasculature, which leads to improved drug delivery.6,7 2. What are the indications for the use of bevacizumab that are approved by the US Foo