Altered Network Topology in Patients with Primary Brain Tumors After Fractionated Radiotherapy

Abstract

Radiation therapy (RT) is a critical treatment modality for patients with brain tumors, although it can cause adverse effects. Recent data suggest that brain RT is associated with dose-dependent cortical atrophy, which could disrupt neocortical networks. This study examines whether brain RT affects structural network properties in brain tumor patients. We applied graph theory to MRI-derived cortical thickness estimates of 54 brain tumor patients before and after RT. Cortical surfaces were parcellated into 68 regions and correlation matrices were created for patients pre- and post-RT. Significant changes in graph network properties were tested using nonparametric permutation tests. Linear regressions were conducted to measure the association between dose and changes in nodal network connectivity. Increases in transitivity, modularity, and global efficiency (n = 54, p < 0.0001) were all observed in patients post-RT. Decreases in local efficiency (n = 54, p = 0.007) and clustering coefficient (n = 54, p = 0.005) were seen in regions receiving higher RT doses, including the inferior parietal lobule and rostral anterior cingulate. These findings demonstrate alterations in global and local network topology following RT, characterized by increased segregation of brain regions critical to cognition. These pathological network changes may contribute to the late delayed cognitive impairments observed in many patients following brain RT.

A comprehensive preclinical assessment of late-term imaging markers of radiation-induced brain injury

“…Lower integration was also reflected in the significantly lower regional connectivity associated with CRT. Similar to our results, Bahrami et al 44 also measured a significant increase in transitivity after radiotherapy but contrary to us they observed a significant increase in global efficiency. Discrepancies between these two findings may be attributed to the fact that their study was done in adult brain tumor patients, whereas ours was in a preclinical pediatric rat model that did not include tumor presence and hence no surgery and/or chemotherapy.…”

Alterations of white matter integrity associated with cognitive deficits in patients with glioma

“…Besides, Bahrami et al. also reported altered network topology in patients with primary brain tumors following fractionated radiotherapy, which might contribute to the delayed cognitive impairments observed in patients with brain tumors (Bahrami et al., 2017).…”

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