PATH-27. MOLECULAR, IMAGING, AND SURVIVAL MANIFESTATIONS IN MOLECULAR GLIOBLASTOMAS: INSIGHTS FROM A MULTI-NATIONAL STUDY

Abstract

Abstract Apart from the traditional definition of IDH-wildtype GBM based on histological characteristics, IDH-wildtype diffuse gliomas previously assigned to histological grade 2 or 3 are now defined as IDH-wildtype GBM in the presence of qualifying molecular markers (TERTp mutation, EGFR amplification, or chromosome +7/-10) (“molecular GBM”) in the 2021 WHO classification. However, the clinical significance of molecular GBM is unrevealed. This collaboration aims to comprehensively evaluate the clinical, molecular, imaging characteristics, and prognosis of molecular GBMs in a multi-national dataset and stratify survival. Retrospective chart and imaging review was performed in 258 molecular GBM patients from eight centers across three continents. Clinical, molecular, imaging, and survival characteristics were analyzed. The median age of molecular GBM patients was 58 years (range: 23-83) with 139 males, with TERTp mutation (83 of 214 [38.8%]), EGFR amplification (160 of 204 [78.4%]), and chromosome +7/-10 (82 of 143 patients [57.3%]). The majority of tumors were located at the frontal and temporal lobes (48.4%) and exhibited non-contrast-enhancing (CE) tumors (73.7%). Gliomatosis cerebri pattern was shown with 27 patients (12.4%). The median OS was 28.1 months (95% confidence interval 22.1-34.1). There was significantly shorter survival in patients with high Ki-67 index (> 20) compared to those with low Ki-67 index (median OS 19.3 vs. 31.5 months, log-rank test P = 0.002), while no survival differences were found according to histological grade or molecular diagnostics. Survival was significantly shorter in patients with infiltrative imaging appearance compared to those without (median OS 24.7 vs 41.0 months, log-rank test P = 0.014). In conclusion, survival within molecular GBM patients may be heterogeneous and associated with Ki-67 index and infiltrative imaging appearance.