Critical considerations on the combined use of 18F-FDG and 18F-fluoride for PET assessment of metastatic bone disease

18F-FDG PET/CT is a reliable imaging tool in the detection of osseous metastasis in most cases. Adedicated bone scan (including 18F-fluoride PET/CT) may not be indicated in many cancers for the evaluation of osseous metastasis, especially at early stages. Combined use of dual tracers may compromise the imaging quality of both studies, especially for 1sF-FDG PET with respect to its ability to detect lesions in the bone marrow. The authors have no doubt that 18F-fluoride PET may be valuable and provide some additional value in some selected cases and selected cancers, where 18F-FDG is of limited value. However, the value of using the combined approach is limited in most situations. The logical notion, is that for 18F-FDG-avid tumors, there is no evidence in the literature that 18F-fluoride PET/CT detects more osseous lesions than 18F-FDG PET/CT, while for non-t8F-FDc-avid tumors, 18F-FDG PET/CT is not indicated. Both the rare occasions (when both 18F-FDG PET and 18F-fluoride PET are indicated) and the advantages of performing a dual tracer PET remain to be defined.