BRAF mutation marks out specific subgroups of glioma

Abstract

Background: Molecular markers including isocitrate dehydrogenase (IDH) mutation and 1p/19q codeletion have been incorporated into the World Health Organization (WHO) 2016 classification of diffuse gliomas for integrated diagnostic reporting. The prognostic relevance of BRAF mutation among the newly established molecularly defined entities of gliomas remained relatively unexplored. Materials and Methods: We examined BRAF mutation in 578 adult diffuse gliomas and examined the clinical significance of the mutation in five histomolecular subgroups, namely oligodendrogliomas, IDH-mutant and 1p/19q-codeleted (Group I), astrocytomas, IDH- mutant (Group II), astrocytomas, IDH-wild-type (Group III), glioblastoma, IDH-mutant (Group IV), and glioblastoma, IDH-wild type (Group V). Results: Mutation rate of BRAF was 5.9% across the whole cohort and was 4.9%, 7.5%, and 7.0% in Group II, Group III, and Group V gliomas, respectively. Univariate analysis revealed a trend of poor overall survival in BRAF-mutant tumors among Group II gliomas, a trend which was also demonstrated by multivariable analysis. Among Group III and Group V gliomas, BRAF-mutant tumors seemed to exhibit more favorable survival in univariate analysis. Multivariable analysis further demonstrated the favorable prognostic significance of BRAF mutation in Group III (hazard ratio [HR] = 0.31, 95% confidence interval [CI] = 0.10–0.95, P = 0.04) and Group V gliomas (HR = 0.44, 95% CI = 0.18–1.09, P = 0.077). Conclusion: BRAF mutation appears to mark out a small subset of adult infiltrative gliomas with the distinct clinical outcome. Mutational analysis of BRAF can potentially contribute to the clinical risk stratification in the management of glioma patients in the context of the WHO 2016 classification.

Keywords

• BRAF mutation
• clinical stratification
• high-grade glioma
• lower-grade glioma
• prognostic biomarker