NI-09 CLINICAL SIGNIFICANCE OF T2-FLAIR MISMATCH SIGN IN LOWER GRADE GLIOMAS

Lower grade glioma is classified based on genetic information of mutation of IDH1/2 gene and co-deletion of chromosome 1p19q. Knowledge of these genetic information preoperatively is useful for making surgical planning, treatment strategy and prognostication. Recently, T2-FLAIR mismatch sign has been reported to be specific for astrocytoma with IDH mutation (mut) / non-1p19q co-deletion (co-del). This study aims to verify it in our patients. We retrospectively analyzed 152 patients aged over 15 years who were pathologically diagnosed with WHO grade 2 or 3 gliomas from April 2003 to December 2018. We excluded 88 patients without genetic information or without T2-weighted and FLAIR images. T2-FLAIR mismatch sign was defined as in the original description, namely, with homogeneously hyperintense signal on T2-weighted image and a peripheral hyperintense signal with central hypointensity signal on FLAIR image. Among 22 patients with IDH mut / non-1p19q codel, 10 were positive for T2-FLAIR mismatch sign. On the other hand, only one patient was positive for T2-FLAIR mismatch sign respectively in 19 with IDH mut / 1p19q codel and 23 patients with IDH wild-type. Sensitivity, specificity, positive predictive value, and negative predictive value of T2-FLAIR mismatch for the patients with IDH mut / non-1p19q codel are 0.46 (95% confidence interval: 0.24–0.68), 0.95 (0.84–0.99), 0.83 (0.52–0.98). and 0.77 (0.63–0.88), respectively. In 22 patients with IDH mut / non-1p19q codel, we compared 10 patients with and 12 without T2-FLAIR mismatch sign. Median age was 35 and 39 years old. WHO grade 3 was 3 patients each. Tumor location was frontal lobe in 9 (90%) and 10 patients (83%). A statistically significant difference was not found in these factors. PFS and OS were not reached in both groups. The specificity of the T2-FLAIR mismatch sign for astrocytoma with IDH mut / non-1p19q codel was very high, which may be helpful as preoperative imaging marker.