Altered structural networks and cognitive functioning in long-term survivors of pediatric brain tumors

Pediatric brain tumor (PBT) survivors frequently exhibit long-term changes in brain network organization and cognition. This study investigated structural brain networks among PBT survivors, exploring the potential influence of radiotherapy during childhood. Cognitive assessments and MRIs were acquired in 20 irradiated and 26 non-irradiated PBT survivors, and 47 healthy controls. Multi-shell diffusion-weighted MRIs were processed to perform tractography and construct weighted graphs. Whole-brain and local graph measures, including hub scores, were calculated. Group differences in cognitive performance and network measures were analyzed using ANOVA or Kruskal-Wallis. Additionally, the susceptibility of hub regions to reorganization and their relationship to cognition were explored. PBT survivors showed poorer performance on the Peabody Picture Vocabulary Task, some Wechsler Adult Intelligence Scale subtests, and figure tapping task of the Amsterdam Neuropsychologic Tasks. Structural network analyses revealed higher whole-brain clustering coefficients in both survivor groups. Locally, clustering coefficients were higher in several regions, particularly in irradiated survivors. Although hub locations were largely preserved, their relative strength showed variability. Differences in local graph measures were more frequently significant in hub regions with higher hub scores. These findings indicate that survivors' structural brain networks undergo reorganization following a PBT and its treatment, especially if survivors had received radiotherapy. Clustering coefficient emerged as the most prominently altered network measure, which was linked to cognitive performance, particularly in hub regions. These results highlight the potential role of structural brain networks to unravel the cause of long-term cognitive outcomes in PBT survivors.