Abstract
Background:
Overall, gliomas harboring 1p19q co-deletion (oligodendrogliomas in the future WHO classification) have better prognosis and better response to treatments compared to their non 1p/19q co-deleted counterparts. However, some of these tumors have disconcerting poor outcome. We have recently shown that chromosome arm 9p loss of heterozygosity (9pLOH) participates to identify some but not all oligodendrogliomas with an aggressive clinical behavior. In parallel, TERT promoter (TERTp) mutations have been recently described as the most frequent mutations in oligodendrogliomas.
Objectives:
We sought to study the potential clinical significance of TERTp mutational status in oligodendrogliomas.
Material and methods:
224 anaplastic oligodendrogliomas (AO) from the POLA network, were included in the present study. TERT mutational status was obtained using Sanger sequencing and SNP-array. 121 lower grade gliomas exhibiting 1p/19q co-deletion, from the TCGA dataset, were used as the validation cohort. In this latter series, level of TERT expression, obtained by RNA-sequencing, was used as a surrogate marker of TERTp mutation. 1p/19q co-deletion was defined as loss of whole-chromosome arms 1p and 19q using allelic-specific copy number analysis. Overall survivals (OS) were compared using log-rank test in univariate analysis. All covariates with p-value < 0.2 were included in a Cox’s proportional hazard ratio model for multivariate analysis. Statistical tests were two-sided and p-values < 0.05 were interpreted as statistically significant.
Results:
TERTp was wild-type (wt) in 14/224 AO (6.25%) in POLA cohort and in 8/121 (6.6%) in TCGA dataset. TERTp wt is associated with poor OS in univariate analysis in POLA and TCGA cohorts (p=0.032 and p=0.035, respectively). Interestingly, after adjusting for allelic 9p LOH, age (<50 vs. ≥ 50 years), treatment (chemotherapy and radiotherapy versus other treatments) and WHO grade (II vs III), TERTp mutation was an independent favorable prognostic factor in the POLA cohort (p=0.037, HR=3.7 (1.1–13)) and in the TCGA dataset (p=0.01, HR=9.8 (1.6–60)).
Conclusion:
This study identifies TERTp mutation as a novel independent prognostic biomarker in oligodendrogliomas toward a better stratification of this tumor type.
Acknowledgements: The results shown here are in whole or part based upon data generated by the TCGA Research Network: http://cancergenome.nih.gov/. La Ligue Nationale Contre La Cancer. The Institut Universitaire de Cancérologie (IUC). The program Investissements d’avenir” ANR-10-IAIHU-06. POLA network is supported by Institut National du Cancer.