Radiolabeled amino acids: Basic aspects and clinical applications in oncology

As the applications of metabolic imaging are expanding, radiolabeled amino acids may gain increased clinical interest, This review first describes the basic aspects of amino acid metabolism, then continues with basic aspects of radiolabeled amino acids, and finally describes clinical applications, w ith an emphasis on diagnostic value. A special focus is on C-11-methionine, C-11-tyrosine, and I-123-iodomethyltyrosine, because these have been most used clinically, although their common affinity for the L-transport systems may limit generalization to other classes of amino acids. The theoretic an d preclinical background of amino acid imaging is sound and supports clinic al applications. The fact that amino acid imaging is less influenced by inf lammation may be advantageous in comparison with F-18-FDG PET imaging, alth ough tumor specificity is not absolute. In brain tumor imaging, the use of radiolabeled amino acids is established, the diagnostic accuracy of amino a cid imaging seems adequate, and the diagnostic value seems advantageous. Th e general feasibility of amino acid imaging in other tumor types has suffic iently been shown, but more research is required in larger patient series a nd in well-defined clinical settings.