Oncologic PET tracers beyond [(18)F]FDG and the novel quantitative approaches in PET imaging

In this review, we focus on the oncological applications of positron emission tomography (PET) tracers other than [(18)F]fluoro-2-deoxy-D-glucose (FDG) and the novel quantitative approaches in PET imaging. Oncological non-FDG PET tracers can be broadly categorized into 3 groups: those labeled with (18)F, (11)C and other non-FDG tracers. Fluorine-18 and (11)C are labeled with different amino acids, substrates involved in fatty acid synthesis, protein synthesis, amino acid transport substrate and tracers linked to nucleic acid synthesis. These tracers are also labeled with specific ligands for receptor imaging (i.e. estrogens, dihydrotestosterone or somatostatin). The other non-FDG radiotracers can be labeled with (68)Ga, (60)Cu, (64)Cu, etc. and are aimed to detect cell hypoxia, bone metabolism and receptor. Many of these have shown promising results in the management of various cancers where FDG has limited role. These radiotracers have more specific mechanism of uptake and is likely be investigated in the near future. In the era of fusion imaging, novel approaches for accurate quantitative analysis include partial volume correction for measured values in small lesions, dual-time point and delayed PET imaging, and global metabolic activity for assessment of various stages of disease. Major changes are likely to occur in the future that may overcome deficiencies that are associated with the current quantitative (standardized uptake value) techniques.