Comparison of the amino acid tracers 18F-FET and 18F-DOPA in high-grade glioma patients

Abstract

Results: Visual analysis revealed no difference in tumor uptake pattern between the 2 PET probes. The SUVmean and SUVmax for 18F-FET were higher than those of 18F-DOPA (4.0 ± 2.0 and 4.9 ± 2.3 vs. 3.5 ± 1.6 and 4.3 ± 2.0, respectively; all P < 0.001). TBRs for SUVmean but not for SUVmax were significantly higher for 18F-FET than 18F-DOPA (TBR SUVmean: 3.8 ± 1.7 vs. 3.4 ± 1.2, P = 0.004; TBR SUVmax: 3.3 ± 1.6 and 3.0 ± 1.1, respectively; P = 0.086). 18FDOPA uptake by the basal ganglia was present (SUVmean, 2.6 ± 0.7) but did not affect tumor visualization. Methods: Thirty 18F-FET and 18F-DOPA PET/CT scans were obtained before surgery or biopsy in 27 patients with high clinical suspicion for primary or recurrent HGG (5 primary, 22 recurrent tumors). 18F-FET and 18F-DOPA PET/CT images were compared visually and semi-quantitatively (maximum standardized uptake value [SUVmax], mean SUV [SUVmean]). Background (SUVmax and SUVmean) and tumor-to-background ratios (TBRs) were calculated for both PET probes. The degree of 18F-DOPA uptake in the basal ganglia (SUVmean) was also assessed. Conclusion: Whereas visual analysis revealed no significant differences in uptake pattern for 18F-FET and 18F-DOPA in patients with primary or recurrent HGG, both SUVs and TBRs for SUVmean were significantly higher for 18F-FET. However, regarding tumor delineation, both tracers performed equally well and seem equally feasible for imaging of primary and recurrent HGG. These findings suggest that both PET probes can be used based on availability in multicenter trials. High-grade gliomas (HGGs) are the most common malignant primary tumors of the central nervous system. PET probes of amino acid transport such as O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET), 3,4- dihydroxy-6-18F-fluoro-L-phenylalanine (18F-DOPA), and 11C-methionine (11C-MET) detect primary and recurrent tumors with a high accuracy. 18F-FET is predominantly used in Europe, whereas amino acid transport imaging is infrequently done in the United States. The aim of this study was to determine whether 18F-FET and 18F-DOPA PET/CT provide comparable information in HGG.