Diagnostic performance of fast brain MRI compared to routine clinical MRI in patients with glioma grade 3 and 4 -a pilot study

BACKGROUND AND PURPOSE: EPIMix is a fast brain MRI technique not previously investigated in patients with glioma grades 3 and 4. This pilot study aimed to investigate the diagnostic performance of EPIMix in the radiological treatment evaluation of adult patients with glioma grades 3 and 4 compared to routine clinical MRI (rcMRI).

MATERIALS AND METHODS: Patients with glioma grades 3 and 4 investigated with rcMRI and EPIMix were retrospectively included in the study. Three readers (R1–3) participated in the radiological assessment applying Response Assessment for Neuro-oncology Criteria (RANO 2.0), of which two (R1–2) independently evaluated EPIMix and later rcMRI by measuring contrast-enhancing and non-contrastenhancing tumor regions at each follow-up. For cases with discrepant evaluations, an unblinded side-by-side (EPIMix and rcMRI) reading was performed together with a third reader (R3). Comparisons between methods (EPIMix vs. rcMRI) were performed using Weighted Cohen’s kappa. The sensitivity and specificity to detect tumor progression (PD) on a follow-up scan were calculated for EPIMix compared to rcMRI with receiver operating characteristic (ROC) curves to assess the area under the curve (AUC).

RESULTS: In 35 patients (mean age 53, 31% females), a total of 93 MRIs encompassing 58 follow-up investigations showed PD at blinded reading in 33% of EPIMix (19/58, R1–2), while in 31% (18/58 exams, R1), and 34% (20/58 exams, R2) of rcMRI. An almost perfect agreement for tumor category assessment was found between EPIMix and rcMRI (EPIMixR1 vs. rcMRIR1 ϰ= 0.96; EPIMixR2 vs. rcMRIR2 ϰ= 0.89). The sensitivity for EPIMix to detect PD was 1.00 (0.81–1.00) for R1 and 0.90 (0.68–0.99) for R2, while the specificity was 0.97 (0.86–1.00) for R1–2. The AUC for PD was 0.99 for R1 (EPIMixR1 vs. rcMRIR1) and 0.94 for R2 (EPIMixR2 vs. rcMRIR2), DeLong’s test AUCR1 vs. AUCR2 p=0.20 (R1–2).

CONCLUSIONS: In this pilot study, EPIMix was used as a fast MRI alternative for treatment evaluation of patients with glioma grades 3 and 4, with high, but slightly lower diagnostic performance than rcMRI.

ABBREVIATIONS: CR = complete response; EPIMix = multi-contrast echo-planar imaging-based technique; PD = progressive disease; PR = partial response; RANO = response assessment in neuro-oncology; R1 = reader 1; R2 = reader 2; R3 = reader 3; rcMRI = routine clinical MRI; SD = stable disease.