P01.25.A LOCOREGIONAL DISTRIBUTION OF [18F]FET PET HYPERMETABOLIC FOCI IN DIFFUSE LOWER-GRADE INSULAR GLIOMA: A POTENTIAL LINK TO CANCER NEUROSCIENCE

Abstract BACKGROUND Insular gliomas pose great challenges to maximal safe resection. Perioperative morbidity is comparably high due to adjacent functional structures and vascular anatomy. Synaptic density in limbic/ paralimbic structures, including the insula, is known to be high. According to current concepts of cancer neuroscience, functional connectivity may drive tumor proliferation. Conversely, glioma increase neuronal excitability. This study investigates [18F]FET PET hypermetabolic foci distribution in insular gliomas to explore a potential link between cancer neuroscience and metabolic heterogeneity. MATERIAL AND METHODS A monocentric retrospective analysis identifies therapy-naïve patients with preoperative [18F]FET PET, that were later diagnosed with diffuse lower-grade glioma (DLGG). Fisher’s exact test is performed to compare insular glioma with other DLGG regarding location of hypermetabolic foci (background SUVmean x 1.6). Insular gliomas are categorized according to Yasargil’s classification for limbic/ paralimbic tumors. RESULTS Thirty-five (100%) patients with insular glioma, comprising 5 patients (14%) with tumors restricted to the insula exclusively, 20 patients (57%) with tumors extending to adjacent paralimbic structures (Yasargil type 5A), and 7 patients (20%) with tumors extending to limbic structures (Yasargil Type 5B), were included. There was no significant difference in the prevalence of [18F]FET hypermetabolic foci between insular gliomas and other lobar DLGG (p = 0.63), with foci identified in 75% of insular gliomas versus 78% in other DLGG. Of all insular gliomas, 19% exhibited [18F]FET hypermetabolic foci within the insula. In type 5A and 5B tumors, hotspots were predominantly located in paralimbic (52%) and limbic (28%) regions. There was no significant correlation of tumor heterogeneity and locoregional distribution within the group of insular gliomas. CONCLUSION This data demonstrates high intratumoral heterogeneity in the group of insular gliomas. However, theoretical high synaptic density in this particular anatomical region does not translate into of [18F]FET hypermetabolic foci distribution. An ongoing study evaluates locoregional distribiton of hypermetabolic foci in lobar DLGG.