P18.24.A GLIOBLASTOMA INVASION OF NEURAL STEM CELL REGIONS; MOLECULAR PATTERNS AND SURVIVAL RATES

Abstract BACKGROUND Glioblastoma is a very aggressive form of brain cancer and poses a challenge in treatment due to its profound heterogeneity and capacity for extensive infiltration into the brain parenchyma. Research has shown glioblastomas in close proximity to the ependyma have poorer survival rates. Therefore, our aim was to identify distinct molecular features of grade 4 glioma invading ependyma of lateral ventricles and neural stem cell region and the survival prognosis of these patients. MATERIAL AND METHODS Retrospective review of 180 patients with a new histologically confirmed diagnosis of grade 4 glioma between 2018 and 2019. Patients excluded if less than 18-years-old, did not have a histological diagnosis, or had missing data. Analysis of anonymised patient data were conducted with ethical consent from NHS GGC Caldicott Guardian. SPSS version-28 used for statistical analysis. RESULTS Average age of all patients was 59 +/-12.3 years with 54% male and 46% female. 170 tumours were identified as IDH-wildtype (IDHw), while 10 were IDH-mutant (IDHm). Of the total 180 patients, 77 tumours contacted the ependyma, with 10.4% being IDHm and 89.6% IDHw. 103 tumours were identified as ependymal non-contacting with 2% being IDHm and 98% IDHw. Statistically significance association found between IDH mutations and ependymal contact (p-value 0.02). For both groups, majority of the tumours were unmethylated, with 57% for contacting and 65% for non-contacting tumours. However, no statistically significant associations were observed between MGMT methylation status and ependymal-contact (p-value 0.35). For IDHw glioblastomas, over half of the tumours for ependymal contact and ependymal non-contact were unmethylated (61% and 65% respectively). Mean overall survival (OS) for all patients was 16.6 (CI 19.0, 14.1) months. OS was lower in ependymal-contact tumours compared to non-ependymal contacting tumours (14.9 months compared to 17.5 months respectively, however this was not significant (p-value 0.11). Sub-analysis of IDHw glioblastomas showed reduced survival by ependymal contact with mean OS of 11.9 months compared to 17.4 months for non-contacting IDHw tumours (p-value 0.004). Mean epicentre distance for ependymal contacting MGMT methylated tumours was 17.7mm compared to 15.6mm for MGMT unmethylated contacting tumours. Statistically significant association found between epicentre distance and methylation status of ependymal-contacting tumours (p-value 0.008). No statistically significant associations found between epicentre distance and IDH status of ependymal-contacting tumours (p-value 0.23). CONCLUSION We have found that ependymal contacting tumours are more likely to be IDHw and MGMT unmethylated. Adjusted analysis showed ependymal-contact to lower survival rates and IDHw contacting tumours to also have poorer survival outcomes.