Tumor recurrence patterns in eloquent glioma after microsurgical resection and adjuvant radiochemotherapy

Background Evidence on the influence of eloquent brain areas on the effectiveness and side effects of radio-therapy (RT) remains limited. This study evaluated the relationship between eloquent brain regions, radiation dose, and tumor recurrence patterns in glioma patients. Methods Preoperative navigated transcranial magnetic stimulation (nTMS) mapping of language and motor function, complemented by nTMS-based tractography, was performed. Magnetic resonance imaging of tumor recurrence was co-registered with RT treatment plans and functional nTMS data. Tumor growth direction, radiation dose to eloquent structures, and clinical outcomes were analyzed. Results Seventy-two patients with glioblastoma, aged 57.7 ± 14.8 years, were included. Tumor recurrence toward eloquent brain areas, assessed either by volumetric or linear measurements, indicated growth affecting motor function in 68.1% and language function in 79.3% of patients. Following RT, new motor deficits occurred in 3/48 patients (6.3%) and language deterioration in 3/20 (15.0%). The mean dose to the corticospinal tract was 10.1 Gy in patients with motor decline versus 3.7 Gy in those without (P = .137). For language fiber tracts, corresponding doses were 34.1 Gy and 15.1 Gy (P = .073). Conclusions Tumor recurrence toward eloquent brain areas was observed, with high radiation doses to eloquent brain areas being associated with higher rates of neurological deterioration. These findings create an ambiguous situation regarding the application of high radiation doses to the resection cavity facing eloquent brain areas while simultaneously ensuring optimal dose gradients to spare those.