Background: Bevacizumab was approved by the FDA for the treatment of recurrent or progressive glioblastoma (GBM). Imaging responses are typically assessed by gadolinium-enhanced MRI. We sought to determine the significance of qualitative diffusion signature (manifest as variable degree of dark signal) on ADC maps in recurrent gliomas after treatment with bevacizumab. Methods: We performed an institutional review board (IRB) approved retrospective study on patients who underwent MRI of the brain after 8 weeks of receiving bevacizumab for recurrent glioma. Patients were divided into three groups based on qualitative diffusion signature: (I) lesion not bright on diffusion weighted imaging (DWI) suggestive of no restricted diffusion (FDR0); (II) 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); and (III) 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: Based on the qualitative signal on diffusion weighted sequences after bevacizumab therapy, total number of patients in group (I) were 14 (36%), in group (II) were 17 (44%); and in group (III) were 8 (20%). 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). On simultaneous comparison of survival differences in all three groups by Kaplan-Meier analysis, group (II) was significant in predicting survival with P values for the log-rank tests <0.033. Conclusions: In patients with recurrent glioma treated with bevacizumab, the presence of homogenous dark signal (FDRn) on ADC maps at 8 weeks follow-up MRI correlated with a longer survival. Thus, use of this qualitative diffusion signature in adjunct to contrast enhanced MRI may have the widest potential impact on routine clinical care for patients with recurrent high-grade gliomas. However, prospective studies analysing its predictive value are warranted.
All Science Journal Classification (ASJC) codes
- Radiology Nuclear Medicine and imaging