Introduction: In our study we aimed assessing the correlation of metabolic information on 11C-methionine PET and biological data in patients affected by primary brain tumor and eligible for surgical resection.
Methods: Data deriving from 54 consecutive patients (M:F=34:20; mean age 45, range 19-77 years) affected by pathologically proven gliomas and referred to our institution for primary tumor resection were analyzed. Patients underwent pre-surgical 11C-methionine PET performed according to standard procedure and in all cases semi-quantitative and quantitative analyses were obtained considering SUVmax, SUVratio, and whole tumor metabolic activity (WTMA), expressed as a product of metabolic tumor volume and lesion SUVmean. Functional data on PET were then correlated with biological information obtained by histology (WHO grade/MIB1) and gene profiling, including isocitrate dehydrogenase 1 gene (IDH1) mutation, 1p/19q co-deletion and O6-methylguanine–DNA methyltransferase (MGMT) promoter methylation.
Results: We analysed 23 grade II low-grade gliomas (LGG), and 31 high-grade gliomas (HGG: 16 grade III and 15 grade IV). Based on semi-quantitative and quantitative analysis, we determined a statistically significant correlation between SUVmax, SUVratio and WTMA versus tumor grading (p<0.001). In our series we could also define some optimal cut-off points able of accurate differentiation between LGG and HGG, respectively SUVmax >2.8, SUVratio >2.08 and WTMA >6.63. We determined a statistically significant correlation with tumor uptake only for IDH1 mutation, which resulted present in patients with lower SUVmax (mean 5.63 versus 2.32; p=0.003) and SUVratio (mean 2.99 versus 1.86; p=0.002). The correlation was not confirmed for WTMA (p=0.8). In addition, no significant difference was found in tumor grade/MIB1 and IDH1 mutation, 1p/19q co-deletion or MGMT methylation.
Conclusions: Semi-quantitative and quantitative information obtained by 11C-methionine PET significantly correlated with histological grading in primary brain tumors. Among other biological data, only IDH1 mutation resulted correlated to tumor uptake, with a prevailing expression in gliomas with lower SUVmax and SUVratio, suggesting as supposed a better prognosis in these cases.
Patient Care: Better delineation of the metabolic substrate of brain tumors
Learning Objectives: To understand metabolic heterogeneity of primary brain tumors and the relevance of 11C-methionine PET in the presurgical evaluation