The median OS of those tumors harboring mutations in both TERT promoter and IDH1/2, the predominant genetic signature in oligodendrogliomas, was longer than those tumors with an IDH1/2 mutation only, typically seen in Grade II-III astrocytomas (206 months vs. 131 months), but this difference was not statistically significant (log-rank p=0.1754) (Fig. 2A). This evidence concerns the gene IDH1 and oligodendroglioma.