• Nicholas Cho, Chencai Wang, Catalina Raymond, Tania Kaprealian, Matthew Ji, Noriko Salamon, Whitney B Pope, Phioanh L Nghiemphu, Albert Lai, Timothy F Cloughesy, and Benjamin M Ellingson.
• UCLA Brain Tumor Imaging Laboratory (BTIL), Center for Computer Vision and Imaging Biomarkers, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA.
• J. Neurooncol. 2020 May 1; 147 (3): 643-652.

IntroductionThere 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.MethodsForty 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 ADCL, defined as the mean of the lower Gaussian distribution.ResultsThe ipsilesional SVZ had lower ADCL values compared to the contralesional SVZ before treatment (mean difference = 0.025 μm2/ms; P = 0.007). Following chemoradiation, these changes were no longer observed (mean difference = 0.0025 μm2/ms; P > 0.5), as ADCL values of the ipsilesional SVZ increased (mean difference = 0.026 μm2/ms; P = 0.037). An increase in ipsilesional ADCL was associated with shorter progression-free (P = 0.0119) and overall survival (P = 0.0265).ConclusionsThese 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.

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