NIMG-14. THE RELATION BETWEEN T2-FLAIR MISMATCH SIGN AND ADC VALUES REFLECTING PATHOLOGICAL MICROSTRUCTURE IN LOWER-GRADE GLIOMAS

Abstract

Abstract BACKGROUND Although the recent studies have identified “T2-FLAIR mismatch sign” specific to IDH-mutant and 1p/19q-intact gliomas, it is unclear what the mismatch sign represents. We aimed to investigate the mechanisms and validate the clinical utility. METHODS We identified 79 lower-grade gliomas treated at Kobe University Hospital, and classified into three groups: (i) LGGIDH(m),1p19q(-) (n = 18): IDH-mutant and 1p/19q-intact, (ii) LGGIDH(m),1p19q(+) (n=26): IDH-mutant and 1p/19q co-deleted, (iii) LGGIDH(w) (n=35): IDH wild-type. We retrospectively analyzed the relation with apparent diffusion coefficient (ADC) values, metabolites in magnetic resonance spectroscopy and pathological features, and examined the influence of the presence of the mismatch sign on progression-free survival (PFS) and overall survival in LGGIDH(m),1p19q(-). RESULTS Compared to the rim presenting hyperintense on T2WI and FLAIR, the core presenting hyperintense on T2WI and reversely hypointense on FLAIR had significantly higher ADC values (p = 0.002). The core/rim ratios of ADC values were significantly higher in the cases with the mismatch sign (p = 0.001), not depending on IDH status, 1p/19q status and WHO grade. There was no significant difference in metabolites changing between the presence and absence of the mismatch sign. The cases with the mismatch sign in LGGIDH(m),1p19q(-) had abundant microcysts as a pathological feature, and longer PFS than those without the mismatch sign (5-yr PFS: 100% vs 37.5%). Multivariate analysis found the mismatch sign to be the only significant predictor for preferable PFS in LGGIDH(m),1p19q(-) (p = 0.044). CONCLUSION Our study provided the new evidence that the T2-FLAIR mismatch sign had the significantly different ADC values between the core and the rim, suggesting that the mismatch sign reflected the difference of the tumor cellularity and the microenvironment.