ADC maps in non invasive characterization of IDH mutation status in high grade glioma

Introduction The new brain tumor classification (2016 WHO) distinguishes diffuse glioma based on their molecular characteristics of isocitrate dehydroge- nase (IDH) in IDH-mutant, IDH-wild type and IDH NOS (not otherwise specified). The evaluation of IDH mutation status has diagnostic, prog- nostic and therapeutic implications. The aim of this study was to evaluate whether the analysis of ADC maps can non-invasively predict the IDH mutation status. Materials Conventional MR images and ADC maps of 28 patients (11-F, 17-M) with histological confirmed diffuse high-grade glioma (WHO-grade III- IV) were reviewed and correlated with the IDH mutation status (18-MUT, 10-WT). MRI was performed on a 1.5T MR scan (GE-Optima 450). In order to place the ROIs on the solid components of the lesion, the ADC maps were elaborated and co-registered with the T2-w and Gd-enhanced T1-w images. For each tumor 4-5 ROIs were placed and the mean ADC- values (ADCmean) were calculated, choosing the lowest values for each patient. The comparison of the ADCmean values between IDH-MUT and IDH-WT was performed using the Student's "t" test, considering signifi- cant a value of p <0.05. Results The ADCmean values in IDH-WT patients (0.86x10-3mm2/s +/- 0.06) were lower than those of IDH-MUT patients (1.24x10-3mm2 /s +/- 0.19) and the difference between both groups was statistically significant (p <0.01). The value of ADC ≥ 1.01 x10-3mm2/s can be considered as a "cut-off" value to differentiate the IDH mutation status. Conclusions Adding quantitative data such as evaluation of ADC-values to conven- tional MR imaging can be used as a non-invasive marker of specific molecular patterns.