PATH-44. Differences in prognosis due to differences in genetic abnormality background in IDH wild-type glioblastoma

Abstract BACKGROUND In the 2021 WHO Brain Tumor Classification 5th Edition, it became possible to diagnose glioblastoma (GBM) molecularly if a patient had any of the following genetic abnormalities in genetic analysis: TERT promoter mutation, EGFR amplification, and chromosome 7 gain/10 deletion (7+/10-). However, there have been few reports on the clinical features and prognostic impact of these genetic abnormalities in GBM, so we retrospectively examined them in our hospital cases. METHODS Of 56 cases of Grade IV gliomas that underwent surgery at the University of Tokyo Hospital between 2018 and 2022, 51 cases were included, excluding 5 cases (8.9%) with IDH mutations. Clinical and image information was extracted from medical records. Tumor DNA was extracted from tumor samples, and TERT promoter mutations were analyzed by the Sanger method, and EGFR amplification and chromosome 7 gain/10 deletion (7+/10-) were analyzed by the MLPA method. RESULTS The male/female ratio of the 51 cases was 20:31, the mean age at surgery was 64.1 years (range 21-93). TERT mutations were observed in 69.4%, EGFR amplification in 43.3%, and 7+/10- in 46.7%. When comparing survival times only for primary cases, there was no significant difference in overall survival time between the presence or absence of TERT mutations, EGFR amplification, and 7+/10- (p=0.8, 0.2, 0.5). When comparing cases in which none of the three genetic abnormalities were present with cases in which one or more genetic abnormalities were present, no significant difference in survival time was observed (p=0.1). CONCLUSION This study did not find any significant difference in prognosis between the presence or absence of genetic abnormalities in histological GBM. Further research using a larger number of samples is needed to make more accurate prognostic predictions.