Decrease in the apparent diffusion coefficient in peritumoral edema for the assessment of recurrent glioblastoma treated by bevacizumab.

Purposes: Anti-edema effect of bevacizumab was evaluated using the apparent diffusion coefficient (ADC) of peritumoral edema associated with regional cerebral blood flow (rCBV) of the tumor.
Materials and Methods: Nine patients with recurrent glioblastoma were treated using bevacizumab for 4 ∼ 36 months (average 12 months). MRI was performed every 2 months. For each MRI, ADC value, Gd-enhanced area on T1 imaging, area of peritumoral edema on T2 imaging, and rCBV on perfusion imaging were measured. ADC and rCBV values were determined by the use of regions of interest positioned in areas of high signal intensity, as seen on T2-weighted images and ADC maps.
Results: After 2 months of bevacizumab treatment, ADC values and rCBV decreased 49 and 32 % respectively, associated with marked diminishment of the Gd-enhanced area compared with pretreatment. After 6 months, in 5 of the 9 cases, the Gd-enhanced area appeared again with no change in the ADC value and rCBV. In the other four cases, the Gd-enhanced area as well as the ADC value and rCBV returned to the initial status.
Conclusion: The anti-edema effect of bevacizumab for treatment of recurrent glioblastoma that was demonstrated by decreased ADC values and rCBV was dramatic and -prolonged at 6 months even with tumor progression.