IDH1 and oligodendroglioma: In the composed model, both histo-molecular diagnosis (oligodendrogliomas IDH-mutant 1p19q codeleted vs. IDH-mutant astrocytoma, HR 0.28, 95% CI 0.10–0.8, p = 0.02) and initial tumor area assessed as continuous variables after logarithmic conversion (HR 1.82, 95% CI 1.01–3.3, p = 0.05) independently affected patient survival (p = 0.01).