Goyal P, et al. - The importance of qualitative diffusion signature (manifest as variable degree of dark signal) was investigated by experts on ADC maps in recurrent gliomas after treatment with bevacizumab via gadolinium-enhanced MRI. The presence of homogenous dark signal (FDRn) on ADC maps at 8 weeks follow-up MRI exhibited a connection with a longer survival in patients with recurrent glioma treated with bevacizumab. Therefore, use of this qualitative diffusion signature in adjunct to contrast-enhanced MRI possibly demonstrated the widest potential impact on routine clinical care for patients with recurrent high-grade gliomas.

Methods

• An institutional review board (IRB) approved retrospective study was carried out on patients who underwent MRI of the brain after 8 weeks of receiving bevacizumab for recurrent glioma.
• Enrollees were randomized into 3 groups based on qualitative diffusion signature:
• Lesion not bright on diffusion weighted imaging (DWI) suggestive of no restricted diffusion (FDR0);
• Lesion bright on DWI with corresponding homogenous dark signal on apparent diffusion coefficient (ADC) maps suggestive of focal restricted diffusion likely due to bevacizumab induced necrosis (FDRn);
• Lesion bright on DWI with corresponding homogenous faint dark signal on ADC maps suggestive of focal restricted diffusion likely due to viable tumor or heterogeneous spectrum of dark and faint dark signals on ADC maps suggestive of focal restricted diffusion likely due to viable tumor surrounding the bevacizumab induced necrosis (FDRt).

Results

• The total number of patients in group (I) were 14 (36%), in group (II) were 17 (44%); and in group (III) were 8 (20%) according to the qualitative signal on diffusion weighted sequences after bevacizumab therapy.
• As per the data, the median overall survival (OS) from the time of recurrence in patients belonging to group (II) was 364 days vs 183 days for those with group (I) vs 298 days for group (III).
• By comparing the survival differences in all 3 groups through Kaplan-Meier analysis, group (II) appeared to be important in predicting survival with P values for the log-rank tests <0.033.