Advanced diffusion MRI tractography for radiotherapy planning in pediatric brain tumors: A feasibility study

Cranial radiotherapy for pediatric brain tumors can damage white matter tracts (WMTs), adversely impacting brain development. This study evaluated the feasibility of integrating advanced diffusion MRI (dMRI) tractography-derived WMTs into radiotherapy planning for pediatric supratentorial high-grade tumors.

The study retrospectively recruited eight patients (aged 8-16 years) who had undergone surgery and curative-intent radiotherapy from January 2012 to June 2022. The pre-radiotherapy dMRI was utilized to reconstruct the target and 29 individual WMT masks selected based on their relevance to neurocognition, motor, language, and visual functions. These WMT masks were classified into five distance-based priority groups based on their proximity to the tumor, and were subsequently used to re-optimize radiotherapy plans. The dose-volume metrics of the tract-optimized plans were compared to the standard treated plans using the Wilcoxon signed-rank test.

In all cases, the tract-optimized plans achieved a significant dose reduction to the normal brain compared with standard plans across various dose levels (D_mean, D_10%, D_20%, D_50%) by 2.3-3.5 Gy (p < 0.01), equivalent to 5% of the prescription dose. D_mean was reduced for all five WMT groups (p < 0.05), ranging from 3.5-6 Gy, depending on proximity to target, whilst target coverage was maintained (p > 0.05). A D_mean reduction of approximately 1 Gy was achieved to ipsilateral (p < 0.05) and contralateral (p < 0.01) temporal lobes.

Integrating advanced dMRI tractography into radiotherapy plan can enable functional sparing of critical WMTs without compromising target coverage for pediatric supratentorial high-grade brain tumors.