Survival analysis for adult midline glioma: do adult midline gliomas with the h3 k27m mutation really have poor prognosis?

Abstract PURPOSE Since it is known that midline located glioma with H3K27 mutation in children has a disastrous prognosis, in 2016 WHO classification, these tumors were defined as diffuse midline glioma (DMG) and classified as grade IV. A lot of papers about pediatric DMG have been published, but there are not many papers about adult DMG. In this study, we aimed to identify factors affecting the prognosis of adult midline glioma. This is the first paper to study the prognosis of adult DMG according to histological grade and is the largest study to investigate the survival of adult DMG. METHODS We reviewed the chart of adult patients diagnosed with midline glioma with H3K27M mutation after undergoing resection or biopsy among patients who visited our institution between January 2010 and December 2020. Survival analysis was performed according to tumor location, histological grading, Karnofsky Performance Scale (KPS), and age. RESULTS Among the 125 adult midline gliomas we identified, 45 (36.0%) had the H3K27M mutation. As a result of survival analysis performed on 125 adult midline gliomas, low histological grade, KPS ≥ 80, and age ≤ 60 showed significantly better survival. After adjusting for age, the difference in survival between H3K27M mutation and wildtype group was not significant. As a result of survival analysis performed on 45 DMG, low histological grade, KPS ≥ 80, total resection, and concurrent chemoradiation therapy group showed significantly better survival. CONCLUSION In adult midline glioma, disastrous prognosis due to H3K27M mutation was not observed as in children. The prognosis of adult midline gliomas is determined by histological grade, age, KPS, and extent of tumor resection. Therefore, the current WHO classification, which classifies all H3K27M mutant midline gliomas as grade IV regardless of histological diagnoses, is not suitable for adults.