IDH1 Non-Canonical Mutations and Survival in Patients with Glioma.

Background: Non-canonical mutations of the isocitrate dehydrogenase (IDH) genes have been described in about 20-25% and 5-12% of patients with WHO grade II and III gliomas, respectively. To date, the prognostic value of these rare mutations is still a topic of debate.

Methods: We selected patients with WHO grade II and III gliomas and IDH1 mutations with available tissue samples for next-generation sequencing. The clinical outcomes and baseline behaviors of patients with canonical IDH1 R132H and non-canonical IDH1 mutations were compared.

Results: We evaluated 433 patients harboring IDH1 mutations. Three hundred and ninety patients (90.1%) had a canonical IDH1 R132H mutation while 43 patients (9.9%) had a non-canonical IDH1 mutation. Compared to those with the IDH1 canonical mutation, patients with non-canonical mutations were younger ( < 0.001) and less frequently presented the 1p19q codeletion ( = 0.017). Multivariate analysis confirmed that the extension of surgery ( = 0.003), the presence of the 1p19q codeletion ( = 0.001), and the presence of a non-canonical mutation ( = 0.041) were variables correlated with improved overall survival.

Conclusion: the presence of non-canonical IDH1 mutations could be associated with improved survival among patients with IDH1 mutated grade II-III glioma.