cis-4-[18F]-Fluoro-L-proline fails to detect peripheral tumors in humans

System A amino acid transport is increased in transformed in(] malignant cells. The amino acid cis-4-[F-18]-Fluoro-L-proline (cis-[F-18]Fpro) has been shown to be a Substrate of the System A amino acid carrier. In this pilot Study, we investigated the diagnostic potential of cis-[F-18]Fpro ill patients with Various tumors in comparison with [F-18]-fluorodeoxyglucose-positron emission tomography (FDG-PET). Methods: Eight patients (seven females, one male, age range 43-77 years) with large primary, recurrent or metastatic tumors of different histologies Were included ill this Study. One patient had a recurrent non-Hodgkin lymphoma; two patients, metastatic colon or rectal cancer; one, a metastatic endometrial cancer; one, a multiple myeloma; one, an Ewing sarcoma; one, a metastatic breast cancer and one, a gastrointestinal stromal tumor. PET scans Of the trunk were acquired at 1 h after intravenous injection of 400 MBq cis-[F-18]FPro and compared to PET scans with [F-18]FDG. Results: None of the tumors or metastatic lesions in this series of patients demonstrated relevant uptake of cis-[F-18]Fpro. In contrast, all tumors With exception of the multiple myeloma showed all intensive Uptake of [F-18]FDG. The mean standardized uptake value cis-[F-18]Fpro in the tumor or metastases was significantly lower than that of [F-18]FDG uptake (1.7 +/- 0.6 vs. 5.7 +/- 3.0; n=8; P<.01). Conclusion: Although other System A-specific tracers have shown relevant tumor uptake, cis-[F-18]FPro fails to detect most types of human tumors. Based oil these results, we cannot recommend a further evaluation of this tracer as a tumor-seeking agent. (c) 2008 Elsevier Inc. All rights reserved.