T2-FLAIR mismatch sign correlates with 11 C-methionine uptake in lower-grade diffuse gliomas

Purpose The T2-FLAIR mismatch sign is recognized as an imaging finding highly suggestive of IDH -mutant astrocytomas. This study was designed to determine whether the T2-FLAIR mismatch sign correlates with uptake of 11 C-methionine in lower-grade gliomas. Methods We included 78 histopathologically verified lower-grade gliomas (grade 2: 31 cases, grade 3: 47 cases) in this study. 78 patients underwent 11 C-methionine positron emission tomography (MET-PET) scans and magnetic resonance (MR) imaging scans prior to histological diagnosis. The tumor-to-normal ratio (T/N) of 11 C-methionine uptake was calculated by dividing the maximum standardized uptake value (SUV) for the tumor by the mean SUV of the normal brain. MR imaging scans were evaluated for the presence of the T2-FLAIR mismatch sign by three independent reviewers. We compared molecular status, the T2-FLAIR mismatch sign and 11 C-methionine uptake among patients with different lower-grade glioma molecular types. Results The 78 lower-grade gliomas were assigned to one of three molecular groups: Group A ( IDH -mutant and 1p/19q non-codeleted, n = 22), Group O ( IDH -mutant and 1p/19q codeleted, n = 20), and Group W ( IDH wildtype, n = 36). T2-FLAIR mismatch was found in 16 cases (20.5%) that were comprised of 8 (36.4%), 0 (0%), 8 (22.2%) cases in the molecular group A, O and W, respectively. The median T/N ratio of MET-PET in tumors with T2-FLAIR mismatch was 1.50, which was significantly lower than that of tumors without T2-FLAIR mismatch (1.83, p < 0.001, Mann-Whitney U test). In the Groups A and W (excluding Group O), the median T/N ratio on MET-PET in groups A and W (but not group O) with T2-FLAIR mismatch was 1.50, which was significantly lower than that of tumors without T2-FLAIR mismatch (1.81, p = 0.002, Mann-Whitney U test). Conclusion The T2-FLAIR mismatch sign correlated with lower 11 C-methionine uptake in lower grade gliomas.