Telomerase Reverse Transcriptase Promoter Mutations in A Cohort Of Adult Gliomas – Clinicopathological Correlates

Background: Introduction: Gliomas were previously classified histologically, although now the latest WHO classification incorporates several molecular markers to classify these. Detection of TERT promoter mutations is assuming increased importance due to its relevance to prognostication. Objective: The aim of this study was to determine the frequency of TERT promoter mutations, association of TERT promoter mutations with other molecular alterations and to assess the role of TERT promoter mutations in overall survival and progression-free survival in relation to histological and molecular glioma subtypes. Materials and Methods: This study analyzed a cohort of 107 adult patients with diffuse gliomas, WHO grades II and III and glioblastoma, by immunohistochemistry for IDH and ATRX mutations, FISH for 1p/19q co-deletions and PCR sequencing for TERT promoter mutation. Further, five glioma molecular sub-groups were derived using three molecular alteration and included the sub-groups with: i) IDH mutations only, ii) IDH and TERT mutations only, iii) IDH and 1p/19q co-deletion only, iv) Triple negative, and v) Triple positive. Results: IDH mutations and 1p/19q co-deletions were individually and significantly associated with an improved progression free (P = 0.001 and P = 0.002, respectively) and overall survival (P = 0.000 and P = 0.005, respectively) in the present cohort of gliomas. TERT promoter mutations occurred frequently in anaplastic oligodendrogliomas (94%), oligodendrogliomas (87.5%) and glioblastomas (54%). Sub-division into molecular sub-groups showed that the triple-positive tumors carried the best prognosis, followed by IDH only, triple negative and finally the TERT mutation only tumors (P < 0.000). Conclusion: This indicates that sub-classification using these molecular markers separates tumors into prognostically relevant categories.