Diffusion MRI changes in the anterior subventricular zone following chemoradiation in glioblastoma with posterior ventricular involvement

Introduction There is growing evidence that the subventricular zone (SVZ) plays a key role in glioblastoma (GBM) tumorigenesis. However, little is known regarding how the SVZ, which is a harbor for adult neural stem cells, may be influenced by chemoradiation. The current diffusion-weighted imaging (DWI) study explored ipsilateral and contralateral alterations in the anterior SVZ in GBM patients with posterior enhancing lesions following chemoradiation. Methods Forty GBM patients with tumor involvement in the posterior SVZ (mean age = 57 ± 10; left-hemisphere N = 25; right-hemisphere N = 15) were evaluated using DWI before and after chemoradiation. Regions-of-interest were drawn on the ipsilesional and contralesional anterior SVZ on apparent diffusion coefficient (ADC) maps for both timepoints. ADC histogram analysis was performed by modeling a bimodal, double Gaussian distribution to obtain ADC L , defined as the mean of the lower Gaussian distribution. Results The ipsilesional SVZ had lower ADC L values compared to the contralesional SVZ before treatment (mean difference = 0.025 μm 2 /ms; P = 0.007). Following chemoradiation, these changes were no longer observed (mean difference = 0.0025 μm 2 /ms; P > 0.5), as ADC L values of the ipsilesional SVZ increased (mean difference = 0.026 μm 2 /ms; P = 0.037). An increase in ipsilesional ADC L was associated with shorter progression-free (P = 0.0119) and overall survival (P = 0.0265). Conclusions These preliminary observations suggest baseline asymmetry as well as asymmetric changes in the SVZ proximal (ipsilesional) to the tumor with respect to contralesional SVZ regions may be present in GBM, potentially implicating this region in tumorigenesis and/or treatment resistance.