Diffusion tensor image analysis along the perivascular space may serve as a potential biomarker for differentiating glioma recurrence from pseudoprogression: a preliminary study

Background: Diffusion tensor image analysis along the perivascular space (DTI-ALPS) is a non-invasive technique used to investigate alterations in glymphatic system (GS) function related to glioma. This study aimed to investigate the potential of DTI-ALPS in differentiating tumor recurrence (TR) from pseudoprogression (PsP) in glioma patients and the added value of the ALPS index to diffusion tensor imaging (DTI)-derived metrics. Methods: This retrospective study included 72 patients with histologically proven unihemispheric glioma at initial diagnosis who developed new or persisting enhancing lesions (35 with TR and 37 with PsP) on brain magnetic resonance imaging (MRI) after the completion of chemoradiation following gross total resection (GTR), and 34 matched healthy controls (HCs). Ipsilateral ALPS index, contralateral ALPS index, fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated. Group comparisons were made between glioma patients and controls, as well as between TR and PsP. Each DTI metric and ALPS index was assessed via receiver operating characteristic (ROC) analysis in terms of differentiating TR from PsP. Results: Both the ipsilateral and contralateral ALPS indices in the TR group were significantly decreased compared with those in the HC group (ipsilateral: 1.22±0.16 vs. 1.55±0.17; P