Glioma PET: Radiotracers DOPA and FET go head to head

In a direct visual and quantitative comparison of F-18 FET and F-18 DOPA in primary glioma, FET provided more quantitative characterization, but both were successful for tumor delineation, according to a review published Aug. 14 in the Journal of Nuclear Medicine.

High-grade gliomas are the most prevalent cancer of the central nervous system. Constantin Lapa, MD, from the department of nuclear medicine, University Hospital Wurzburg, in Wurzburg, Germany, and colleagues evaluated the agents, full names O-(2-F-18-fluoroethyl)-L-tyrosine (F-18 FET) and  3,4-dihydroxy-6-F-18-fluoro-L-phenylalanine (F-18 DOPA) using both visual interpretation and quantitative parameters to see how each performed.

Lapa et al. noted that F-18 FET was more commonly used across Europe, while amino-acid transport imaging is still catching on in the U.S. This agent is yet to be approved by the FDA. And use of F-18 DOPA is slow-growing, as well.

“Few sites in the United States are using F-18 DOPA for brain imaging under an Investigational New Drug application,” the authors noted.

For this study, the researchers conducted 30 PET/CT scans on 27 patients thought to have primary, high-grade gliomas. For the quantitative aspect of imaging, they documented maximum standardized uptake value (SUVmax), mean standard uptake value (SUVmean), background SUV max and mean, tumor-to-background ratios (TBR) and the SUVmean of FET uptake in the basal ganglia.

Results of this prostpective study revealed that no particular difference in visual interpretation was found between the two agents, whereas the SUVs and TBRs for SUVmean were substantially increased in F-18 FET scans.

“F-18 FET showed higher SUVs and TBR for SUVmean in [high-grade gliomas] than F-18 DOPA. However, both tracers depicted all primary and recurrent brain tumors," wrote the researchers. "Given the similar tumor tracer distribution and excellent correlation between F-18 FET and F-18 DOPA SUVs, we conclude that both PET probes of amino acid transport can be used in trials and clinical routine.”

Further study and regulatory approval would need to be finalized before FET and DOPA PET/CT could be fully embraced in clinical practice for neuroimaging of gliomas.