Kaplan-Meier survival curves for progression-free survival within a low-grade glioma group with low and high rCBV (<1.75 and >1.75, respectively; solid lines) demonstrating a significant difference in time to progression in low-grade gliomas stratified by rCBV alone (P < .0001). Similarly, when comparing high-grade gliomas (broken lines), one sees a significant difference in progression with high-versus-low rCBV (<1.75 versus >1.75) (P < .0001). Among subjects with low rCBV (<1.75), there is a significant difference between low- and high-grade gliomas with respect to progression-free survival (P = .047). However, among subjects with high rCBV (> 1.75), progression-free survival is not significantly different for low-versus-high-grade gliomas (P = .266). Reprinted with permission from Radiology (2008;247:490–98). Copyright 2008, Radiological Society of North America.