The T2-FLAIR Mismatch Sign as an Imaging Marker for Non-Enhancing IDH-mutant, 1p/19q-intact Lower Grade Glioma: A Validation Study

Abstract

Background

The purpose of this study was to assess the reproducibility of the previously described T2-FLAIR mismatch sign as a specific imaging marker in non-enhancing isocitrate dehydrogenase (IDH) mutant, 1p/19q non-codeleted lower grade glioma (LGG), encompassing both diffuse and anaplastic astrocytoma.

Methods

MR scans (n=154) from three separate databases with genotyped LGG were evaluated by two independent reviewers to assess (i) presence/absence of "T2-FLAIR mismatch" sign and (ii) presence/absence of homogenous signal on T2WI. Interrater agreement with Cohen's kappa (κ) was calculated, as well as diagnostic test performance of the T2-FLAIR mismatch sign to identify IDH-mutant astrocytoma.

Results

There was substantial interrater agreement for the T2-FLAIR mismatch sign [κ = 0.75 (0.64, 0.87)], but only fair agreement for T2 homogeneity [κ = 0.38 (0.25-0.52)]. The T2-FLAIR mismatch sign was present in 38 cases (25%) and had a positive predictive value of 100%, negative predictive value of 68%, a sensitivity of 51% and a specificity of 100%.

Conclusions

With a robust interrater agreement, our study confirms that among non-enhancing LGG the T2-FLAIR mismatch sign represents a highly specific imaging marker for IDH-mutant astrocytoma. This non-invasive marker may enable a more informed patient counsel and can aid in the treatment decision processes in a significant proportion of patients presenting with non-enhancing, LGG like lesions.