gms | German Medical Science

Objective: Diffuse gliomas are classified by recurrent mutations in the IDH1/2 and TP53/ATRX genes, the TERT promoter, and chromosome 1p/19q loss. These alterations cluster tumors into different molecular groups with distinct prognoses. Here, we sought to identify the differences in MRI/radiological presentations between lower-grade vs. higher-grade IDH-mutant diffuse gliomas.

Method: Clinical and radiological data of 89 patients; 40 patients with WHO grade II gliomas, 39 patients with WHO grade III gliomas and 10 patients with secondary GBM were collected. Sequencing of IDH1 codon 132, IDH2 codon 172 as well as of the TERT-promoter was performed. Moreover, the 1p/19q-co deletion status was determined in gliomas harboring oligodendroglial components (n=32). Using immunohistochemistry, the MIB-1 index and the p53 over-expression status were detected. All molecular data were correlated to the tumor features on MRI before treatment.

Results: IDH mutations were present in 73 patients (82%; in 34 patients with grade II, 29 patients with grade III gliomas and in all 10 secondary GBM, respectively). TERT mutations were detected in 28 patients (31.4%) and a co-deleted 1p/19q status in 23.6% of the entire group. Both groups of glioma grades II and III with an IDH mutation depicted similar radiological features – in regard to tumor localization, insular involvement, contrast enhancement, tumor heterogeneity, local and/or bilateral infiltration pattern, midline shifting and diffusion restriction – without any significant differences. Significantly more IDH-mutant grade III and IV tumors were bigger than 6 cm in comparison with grade II gliomas) 72% vs. 28%, p=0.034).

Conclusions: Our analysis indicates that IDH-mutant gliomas WHO grades II and III are distinguished primarily by tumor size differences on MR imaging. We further elucidate that in particular contrast enhancement is not a feasible clinical marker to differentiate between grades II and III IDH-mutant gliomas.