Recurrent mutations in the promoter region of telomerase reverse transcriptase 
(TERT) have been found in various cancers including diffuse gliomas. Mutations 
lead to TERT upregulation and are associated with aggressive clinical behavior 
in glioblastomas. However, the clinical significance of TERT promoter mutations 
in lower-grade gliomas remains undetermined. The aim of this study is to 
evaluate the status of TERT promoter and the respective prognostic significance 
in a cohort of 237 lower-grade gliomas comprising grades II and III 
astrocytomas, oligodendrogliomas, and oligoastrocytomas. Mutually exclusive 
mutations in TERT promoter, C228T and C250T, were identified in 16/105 (15%) 
diffuse astrocytomas, 16/63 (25%) anaplastic astrocytomas, 13/18 (72%) 
oligodendrogliomas, 3/3 (100%) anaplastic oligodendrogliomas, 17/45 (38%) 
oligoastrocytomas, and 2/3 (67%) anaplastic oligoastrocytomas. Mutations 
co-occurred with 1p/19q codeletion (P<0.001) and are associated with 
oligodendroglial histology (P<0.001). Kaplan-Meier's survival analysis showed 
that TERT promoter mutation (P=0.037), Isocitrate dehydrogenase (IDH) mutation 
(P<0.001), and 1p/19q codeletion (P<0.001) were associated with favorable 
overall survival (OS). In the subset of 116 IDH-mutated lower-grade gliomas 
lacking 1p/19q codeletion, 19 TERT promoter-mutated tumors exhibited longer 
progression-free survival (PFS) (P=0.027) and OS (P=0.004). Consistent with this 
observation, in the subset of 97 IDH-mutated astrocytomas, 14 TERT 
promoter-mutated tumors showed longer PFS (P=0.001) and OS (P=0.001). In 
contrast, among the subset of 74 IDH wild-type lower-grade gliomas with intact 
1p/19q, TERT promoter mutation was associated with shorter PFS (P=0.001) and OS 
(P=0.001). Similarly, in the subset of 65 IDH wild-type astrocytomas, 16 TERT 
promoter-mutated tumors exhibited unfavorable PFS (P=0.007) and OS (P=0.008). 
Our results indicate that when combined with IDH status, TERT promoter mutation 
contributes to prognostic subgroups of lower-grade astrocytic tumors or 1p/19q 
intact lower-grade gliomas and this may further refine future molecular 
classification of lower-grade gliomas.