HGG-33. Prognostic factors of H3K27M histone-mutant diffuse midline gliomas in patients ≤18yrs

OBJECTIVE：Diffuse midline gliomas associated with high malignancy and poor prognosis. The primary treatment modalities include surgery, radiotherapy and chemotherapy. The purpose of this study was to investigate the prognostic factors of diffuse intracranial midline glioma. METHODS: A retrospective analysis was performed on 44 cases younger than 18 yrs of H3K27M histone-mutant diffuse midline gliomas diagnosed in Guangdong Sanjiu Brain Hospital from November 2017 to November 2021. The median age was 9 years (range:3-18), including 24 males and 20 females, lesions located in thalamus were 9, while in brain stem were 35. Treatment methods: 35 cases received radiotherapy, 9 cases did not. Among the patients who received RT, 26 cases with concurrent chemoradiotherapy + adjuvant chemotherapy, 8 cases with concurrent chemoradiotherapy only, and 1 case only with radiotherapy. Kaplan-meier method was used to calculate overall survival (OS), and log-rank test was used to test. P < 0.05 was considered statistically significant. RESULTS: By January 27, 2022, 13 cases survived, 25 cases died, and 6 cases were lost to follow-up. The median survival time of 44 patients was 6.95 months (range：1-23.5 months). The median survival was 8.4 months in the radiotherapy group vs 3.7 months in the non-radiotherapy group (P＜0.001); The median survival time of radiotherapy without adjuvant chemotherapy vs radiotherapy with adjuvant chemotherapy was 6.2 months vs 9.35 months (P=0.479). CONCLUSION: Radiotherapy can prolong the survival time of diffuse midline glioma in children with H3K27M histone mutant but no survival benefit was observed in patients with concurrent chemotherapy.