10184- MPC-17 CHARACTERISTICS AND OUTCOMES OF DIFFUSE NON-MIDLINE GLIOMAS WITH H3F3A GENE MUTATION IN THE KANSAI MOLECULAR DIAGNOSIS NETWORK FOR CNS TUMORS (KANSAI NETWORK)

Abstract PURPOSE Diffuse gliomas with H3F3A gene mutation such as H3.3 K27M and G34R/V in cerebral hemisphere can be found in diffuse gliomas rarely. These tumors may be called histone H3 K27M-mutant diffuse non-midline gliomas (NDMG) and H3 G34-mutant diffuse hemispheric gliomas (DHG), respectively. This study investigates clinical, radiological and molecular characteristics as well as treatment outcomes of patients with H3 K27-mutant NDMG compared with H3 G34-mutant DHG. METHODS We collected histone H3-mutant diffuse glioma cases at non-midline location and enrolled in Kansai Molecular Diagnosis Network for CNS Tumors. Clinical, radiological pathological characteristics and DNA methylation were analyzed retrospectively and compared between NDMG and DHG cases. Various factors were evaluated to examine their effects on overall survival. RESULTS A total of 16 patients with H3 K27M-mutant NDMG and 9 patients with H3 G34R/V-mutant DHG were included in this study. Patients with NDMG were older than those with DHG (median age = 45 vs. 25 years old). Overall survival times (OS) of patients with NDMG was comparable to those of DHG (median OS = 20.0 vs. 22.5 months). Female gender, preoperative KPS score 80 and over and extensive surgical resection tended to improve prognoses of the patients with these tumors. H3 K27M-mutant NDMGs possess are similar DNA methylation property to H3 K27M-mutant DMGs. CONCLUSIONS Diffuse gliomas harboring histone H3 K27M mutation can arise at cerebral hemisphere in the older adults. H3 K27M-mutant NDMG could be a different tumor type from DMG or DHG defined in CNS WHO 2021.