To assess the preoperative ¹¹C-methionine (¹¹C-MET) PET imaging in glioma grading efficacy and its predictive value for isocitrate dehydrogenase enzyme 1 (IDH1) gene mutation status.

A total of 118 glioma cases (70 males, 48 females; median age 45 years, age range: 10-71 years; Ⅱ grade 65 cases, Ⅲ grade 34 cases, Ⅳ grade 19 cases) received ¹¹C-MET PET imaging in PET Center of Huashan Hospital from February 2012 to November 2017 were retrospectively analyzed. Lesion-based semi-quantitative analysis was conducted on the ¹¹C-MET imaging. Maximum standardized uptake value (SUV_max), peak standardized uptake value (SUV_peak), tumor-to-background ratio (TBR; SUV_max in lesion/mean standardized uptake value (SUV_mean) in normal contralateral cortex) were calculated. Independent-sample t test and one-way analysis of variance were applied to assess the differentiating efficacy of ¹¹C-MET PET imaging for different glioma groups. Based on IDH1 immunohistochemical staining results, predictive efficacy of ¹¹C-MET PET diagnostic parameters on IDH1 mutation status in glioma patients was further analyzed with receiver operating characteristic (ROC) curve analysis.

Low-grade glioma (LGG; grade Ⅱ) group showed significant differences from high-grade glioma (HGG; grade Ⅲ-Ⅳ) group in SUV_max(2.458±1.100 vs 3.828±1.540; t=5.624, P<0.01), SUV_peak (2.160±0.991 vs 3.261±1.319; t=5.175, P<0.01) and TBR (2.283±0.942vs 3.434±1.395; t=5.328, P<0.01). SUV_max (2.458±1.100, 3.591±1.611 and 4.251±1.343; F=17.67, P<0.01), SUV_peak(2.160±0.991, 3.040±1.335 and 3.656±1.225; F=15.48, P<0.01) and TBR (2.283±0.942, 3.010±1.242 and 4.192±1.358;F=22.73, P<0.01) were different in grade Ⅱ, Ⅲ and Ⅳ glioma subgroups. SUV_max, SUV_peak and TBR all showed significant differences between grade Ⅱ and grade Ⅲ gliomas, grade Ⅱ and grade Ⅳ gliomas, and there were also statistical differences between grade Ⅲ and grade Ⅳ glioma with TBR (all P<0.01). SUV_max indicated the best single-parameter prediction performance (area under curve (AUC) =0.808, z=7.193, P<0.01), while the SUV_max + SUV_peak showed the best performance (AUC=0.852, z=9.115, P<0.01). In the subgroup of grade Ⅱ (n=55), TBR of patients with IDH1 gene mutation (n=41) was lower than that of patients with IDH1 wild-types (n=14; 2.152±0.759 vs 2.793±1.208; t=2.326, P=0.02), while TBR of those with oligodendrogenic components (n=26) was higher than that of patients with IDH1 gene mutation only (n=18; 2.383±0.825 vs 1.854±0.478; t=2.447, P=0.02).

Preoperative semi-quantitative parameters (SUV_max, SUV_peak, TBR) of ¹¹C-MET brain PET imaging have satisfactory grading discrimination performance for glioma patients. SUV_max is the best predictor for IDH1 mutation as a single parameter, while SUV_max + SUV_peak showed the most optimized predictive ability. The oligodendrogenic components in glioma can increase the uptake of ¹¹C-MET, which may affect the effectiveness of ¹¹C-MET in determining glioma grade to some extent.

Glioma; Positron-emission tomography; Methionine; Genes; Mutation; Isocitrate Dehydrogenase