NCOG-04. MEMORY TRACT SPARING USING DIFFUSE TENSOR IMAGING IN RADIATION PLANNING OF PRIMARY BRAIN TUMORS

Abstract INTRODUCTION Radiation therapy (RT) is a critical treatment modality for both primary and metastatic brain tumors, yet approximately 30% of patients experience cognitive decline post-radiotherapy. This cognitive toxicity is linked to low radiation doses affecting neural stem cells in the hippocampal dentate gyrus. Hippocampal Avoidance (HA)-Whole Brain Radiotherapy (WBRT) combined with Memantine has shown promising outcomes in preserving cognitive function and quality of life (QOL) in patients with brain metastases, suggesting it should be the standard of care for those with good performance status and no hippocampal metastases. METHODS We conducted a prospective trial approved by the IRB (SMC0307-23), including patients aged 18 and above with primary brain tumors post-resection or biopsy. Exclusion criteria included multifocal glioma crossing to the other hemisphere. RT was delivered to a total dose of 60Gy in 30 fractions with concomitant TMZ. Diffusion tensor imaging (DTI) was performed to map hippocampal-associated white matter tracts. Memory fiber tracts and hippocampi were contoured and integrated into RT planning using Eclipse treatment planning software. Dosimetric analyses compared two plans: one with memory fiber constraints and one without. RESULTS Twelve patients with low-grade gliomas were included, with successful contouring of memory fibers and hippocampi. VMAT treatment plans met dose constraints for memory fibers, with an average mean dose of 10.1 Gy. The average MoCA score before RT was 27.1 and 26.4 at six months post-treatment, with a p-value of 0.07. Excluding one patient, the scores were 27.1 and 26.6, respectively (p=0.13). CONCLUSION MRI planning using DTI 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.