1-(2-[18F]FLUOROETHYL)-L-Tryptophan

Xenograft mouse models of glioblastoma and metastatic brain tumors (from lung and breast cancer) were developed by subcutaneous implantation of patient tumor fragments. Dynamic PET scans with ¹⁸F-FETrp and ¹¹C-AMT were obtained for mice bearing human brain tumors 1-7 d apart. The biodistribution and tumoral SUVs for both tracers were compared.

¹⁸F-FETrp showed prominent uptake in the pancreas and no bone uptake, whereas ¹¹C-AMT showed higher uptake in the kidneys. Both tracers showed uptake in the xenograft tumors, with a plateau of approximately 30 min after injection; however, ¹⁸F-FETrp showed higher tumoral SUV than ¹¹C-AMT in all 3 tumor types tested. The radiation dosimetry for ¹⁸F-FETrp determined from the mouse data compared favorably with the clinical ¹⁸F-FDG PET tracer.

¹⁸F-FETrp tumoral uptake, biodistribution, and radiation dosimetry data provide strong preclinical evidence that this new radiotracer warrants further studies that may lead to a broadly applicable molecular imaging tool to examine abnormal tryptophan metabolism in human tumors.