Bevacizumab for glioblastoma What can we learn from patterns of progression?

Glioblastoma is the most common type of malignant primary brain tumor and has a median survival of only 14.6-16 months.(1,2) For patients whose tumors progress after standard radiotherapy with concomitant and adjuvant temozolomide chemotherapy, the treatment options are limited. Because glioblastomas are highly vascular tumors, therapies that target angiogenesis have generated substantial interest. In 2009, bevacizumab, a humanized monoclonal antibody against vascular endothelial growth factor, received accelerated approval from the US Food and Drug Administration for treatment of recurrent glioblastomas based on 2 phase II trials showing improved response rates and 6-month progression-free survival (PFS) compared to historical controls.(3,4) However, the benefits of bevacizumab are transient, and tumors progress after a median of only 3-5 months.(3,4) Once tumors progress on bevacizumab, further treatments are of little or no benefit.(5