P10.11.A CHARACTERISTICS OF DIFFUSE MIDLINE GLIOMA WITH H3 K27M MUTATION IN ADULTS

Abstract

Abstract BACKGROUND H3 K27M-mutant diffuse midline gliomas (DMG) occur primarily in children but can also be encountered in adults. Adult H3 K27M-mutant DMG is a still challenging disease with no effective medical therapies. MATERIAL AND METHODS We retrospectively analyzed the characteristics and prognostic factors of 49 adult patients with intracranial midline gliomas treated in Kobe University Hospital from 2006 to 2022. RESULTS The median age at diagnosis in midline gliomas was 50.8 years (range: 17-83 y). All tumors were located in thalamus n=25, brainstem n=10, cerebellum n=14. Isocitrate dehydrogenase 1 (IDH1) and H3 K27M mutation was recognized in 6 and 16 patients, respectively, which was mutually exclusive. In all midline gliomas, the identification of H3 K27M mutation was significantly a poor prognosis factor (median 18.5 months vs 34.2 months, p=0.041). Among IDH1 wild-type midline gliomas, however, H3 K27M-mutant DMG had no worse overall survival (median 18.8 months vs 22.2 months, p=0.805). CONCLUSION H3 K27M-mutant DMG is considered as a distinct WHO Grade 4 regardless of histological features, but the biological properties of H3 K27M mutation is not yet defined in IDH1 wild-type midline gliomas in adults.