10179-NI-8 CLINICORADIOLOGICAL CHARACTERISTICS OF H3 K27-ALTERED THALAMIC GLIOMAS

Abstract

Abstract BACKGROUND Diffuse midline glioma (DMG), H3 K27-altered (CNS WHO grade 4, 2021), exhibits diverse imaging features, and its characteristics have not yet been established. METHODS We retrospectively analyzed the imaging features and progression patterns of cases with H3p.K27M mutation in the thalamus, as part of the Kansai Molecular Diagnosis Network for CNS Tumors. RESULTS Among the H3p.K27M mutation cases accumulated from May 2007 to July 2022 (total 109 cases), 47 cases were located in the thalamus. The main tumor location was as follows: right side 23 cases, left side 19 cases, bilateral 4 cases and unknown 1 case. The tumor border was well-defined in 18 cases (38.3%), indistinct in 26 cases (55.3%), and uncertain in 3 cases (6.4%). Contrast enhancement was observed in 36 cases (76.6%), necrosis in 29 cases (61.7%), cyst formation in 11 cases (23.4%), peritumoral brain edema in 15 cases (31.9%), ventricular enlargement in 28 cases (59.6%), and evidence of cerebrospinal fluid dissemination on imaging in 8 cases (17.0%). The degree of tumor progression from the main tumor to the surrounding area was scored from 1 to 5 (mean: 3.5, median: 4). SURVIVAL RESULTS Among 43 cases with confirmed overall survival (OS) and progression-free survival (PFS), the median OS was 19.2 months (95% CI: 13.2-25.2), and the median PFS was 9.8 months (95% CI: 5.4-14.2). In univariate analysis, favorable prognostic factors were preoperative KPS 80 over(p = 0.007), and tumor progression score of 2 or less (p = 0.01). However, in multivariate analysis, only a tumor progression score of 2 or less remained the sole independent factor (p = 0.03, HR: 3.89, 95% CI: 1.14-13.3). DISCUSSION AND CONCLUSION A large-scale prospective study is needed, but in H3 K27M-mutant thalamic gliomas, the extent of tumor progression before surgery may be a prognostic factor.