NIMG-08. IMAGING FINDINGS AND PROGNOSTIC FACTORS IN DIFFUSE HEMISPHERIC GLIOMA, H3 G34-MUTANT

Abstract INTRODUCTION Diffuse hemispheric glioma, H3 G34-mutant (DHGs), are a newly categorized tumor in pediatric-type diffuse high-grade gliomas in the 2021 World Health Organization classification, with a poor prognosis. DHGs has been reported to occur in less than 1% of all gliomas, but prognostic factors have not been fully investigated in previous studies due to small sample sizes. In this study, we investigated the relationship between clinical factors, including imaging findings, and prognosis in patients with DHGs. METHODS We searched Medline through the PubMed database using two search terms: “G34” and “glioma”, between 1 April 2012 and 1 July 2023. We retrieved articles that described imaging findings and overall survival (OS), and added one DHG case from our institution. We defined midline invasion (MI) as invasion to the contralateral cerebrum, brainstem, corpus callosum, thalamus, and basal ganglia on magnetic resonance imaging. The primary outcome was 12-month survival, estimated using Kaplan–Meier curves and logistic regression. RESULTS A total of 96 patients were included in this study. The median age was 22 years, and the proportion of male patients was 48.4%. Lesions were most frequently located in the frontal lobe (52.6%). MI was positive in 39.6% of all patients. The median OS of all cases was 14.4 months. Univariate logistic regression analysis with 12-month OS as the outcome showed that the MI-positive group had a significantly higher mortality than that in the MI-negative group, and the gross total resection achieved group had a significantly lower mortality than that in the group that underwent biopsy alone. Multivariate logistic regression analysis revealed that MI was an independent prognostic factor in DHGs. CONCLUSIONS Similar to glioblastomas, DHGs have a poor prognosis if they invade deep structures or the contralateral cerebrum; however, safe and maximal tumor resection may prolong survival.