Combination genetic signature stratifies lower-grade gliomas better than histological grade.

We studied if combination genetic signature potentially stratifies lower-grade gliomas better than histology by investigating 214 lower-grade gliomas for IDH1/2 and TERTp mutations, 1p/19q codeletion and EGFR amplification as to their impact on prognostication. Prognostic association of grading was independent of other prognostic variables including age, histological type, IDH1/2, 1p/19q and TERTp status. No single marker, including IDH1/2, superseded grading in prognostication, indicating grading was still a very important tool. Prognosis was most favorable in 31.7% of patients with IDH1/2 mutation and either 1p/19q codeletion or TERTp mutation (IDHmut-OT), intermediate in 45.8% of patients with IDH1/2 mutation only (IDHmut) and 16.9% of patients without any of the alterations (IDHwt), and poorest in 5.6% of patients with wild-type IDH1/2 and either TERTp mutation or EGFR amplification (IDHwt-ET). Our results suggested not all IDH1/2 wild-type lower-grade gliomas are aggressive and additional biomarkers are required to identify glioblastoma-equivalent tumors. Multivariate analysis revealed independent prognostic values of grading and genetic signature. Grade II IDHwt-ET gliomas exhibited shorter survival than IDH1/2 mutated grade III gliomas, suggesting combination genetic signature potentially superseded grading in prognostication. In summary, biomarker-based stratification is useful in the diagnosis and prognostication of lower-grade gliomas, and should be used together with grading.