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2028 Background: According to the 2016 WHO classification of Central Nervous System tumors, the assessment of exon 4 mutations in IDH1 or IDH2 genes is an essential step in the characterization of gliomas. The R132H mutation is the most frequent alteration in IDH1 gene, however other non-canonical IDH mutations have been identified. The aim of this study was to evaluate the prognostic role of IDH non-canonical mutations. Methods: We analyzed our institutional data warehouse for all consecutive patients (pts) with newly diagnosed, histologically proven grade II – IV IDH mutant gliomas. IDH sequencing was performed using the 454 GS-Junior next generation sequencer (NGS) (Roche Diagnostic, Mannheim, Germany). All analyses were performed on DNA from formalin fixed and paraffin embedded (FFPE) specimens. Results: The analysis included 493 pts with IDH mutations. We found 279 (56.6%) grade 2, 173 grade 3 (35.1%) gliomas, and 41 (8.3%) IDH mutant glioblastoma. Canonical IDH1 R132H mutation was found in 428 pts (86.8%). The remaining pts showed IDH2 (3.9%) or IDH 1 non-canonical mutations (mainly R132C, R132G, R132S – 9.3%). Median follow-up time was 80.5 months. Pts with non-canonical mutations showed a younger median age (32 vs 39 years, p < 0.001). Other clinical characteristics and treatments were similar across IDH groups. Median survival was 145 months (95%CI: 137.7 - 152.9) and 198.6 (95%CI 155.2– 242.1) in patients with IDH R132H and non-canonical mutations, respectively (p = 0.013). In multivariate analysis grading (p < 0.001), extent of surgery (p < 0.001), 1p19q codeletion (p = 0.003) and presence of non-canonical mutations (p = 0.022) showed a significant role for improved survival. Conclusions: Detecting non-canonical IDH1 mutations is essential for diagnosis and for prognosis in patients with gliomas. Differential enzymatic activity of non-canonical IDH1 mutations, resulting in different levels 2-hydroxyglutaratecould be the reason of improved survival.

e14057Background: About 21-62% of GBM patients (pts) access to 3rd line therapy. In this setting, there is no defined standard. In this study we evaluated the outcome of pts who received 3rd line t...

2040Background: Low grade gliomas (LGG) are a heterogeneous group of brain primary tumors. The EORTC and the RTOG criteria are the most valuable scores to evaluate risk factors and for treatment de...