Martini M, et al. - Given that vascular endothelial growth factor (VEGF) isoforms, particularly the diffusible VEGF-121, could play a major role in the response of recurrent glioblastoma (GB) to anti-angiogenetic treatment with bevacizumab, researchers tested their hypothesis that circulating VEGF-121 may attenuate the amount of bevacizumab available to target the heavier isoforms of VEGF, which are the most clinically relevant. In the prediction of response to anti-angiogenetic treatment in patients with recurrent GB, quantitative analysis of VEGF-121 isoform in their plasma could be promising.