Memory Tract Sparing Using Diffusion Tensor Imaging in Radiation Planning of Primary Brain Tumors

Purpose: Radiation therapy (RT) is a critical treatment modality for both primary and metastatic brain tumors, yet ∼30% of patients experience cognitive decline post-RT. This cognitive toxicity is linked to low radiation doses affecting the hippocampal dentate gyrus. Hippocampal avoidance-whole brain RT combined with memantine has shown promising outcomes in preserving cognitive function and quality of life in patients with brain metastases. Nowadays, it is the standard of care for those with good performance status and no hippocampal metastases. Methods and Materials: We conducted a prospective trial approved by the institutional review board (SMC0307-23), including patients aged ≥18 years with primary brain tumors postresection or biopsy. Exclusion criteria included multifocal glioma crossing to the other hemisphere. RT was delivered to a total dose of 54 Gy in 30 fractions. Diffusion tensor imaging was performed to map hippocampal-associated white matter tracts. Using Eclipse treatment planning software, memory fiber tracts and hippocampi were contoured and integrated into RT planning. Dosimetric analyses compared 2 plans with memory fiber constraints and 1 without. The primary endpoints were safety and dosimetric feasibility. Results: Twelve patients with low-grade gliomas were included, and the contouring of memory fibers and hippocampi was successful. Volumetric modulated arc therapy (VMAT) treatment plans met-dose constraints for memory fibers, with an average mean dose of 10.1 Gy. The average Montreal Cognitive Assessment score before RT was 27.1 and 26.4 at 8 months post-treatment, with a P value of .07. Excluding 1 patient, the scores were 27.1 and 26.6, respectively (P = .13). Conclusions: Magnetic resonance imaging planning using diffusion tensor imaging for memory fiber detection and incorporation into RT planning via VMAT techniques enables hippocampal and associated white fiber sparing, potentially preserving cognitive function. Preliminary cognitive data are promising, supporting the need for further validation in a larger cohort.