Role of 18F-FDG PET–CT imaging for the detection of an unknown primary tumour: preliminary results in 21 patients

Purpose Metastatic cancer of unknown primary origin is a syndrome characterised by a poor prognosis, with a typical survival rate from diagnosis of no longer than 1 year. Only 20–27% of primary tumours are identified by conventional radiological imaging. By contrast, it has been reported that 18F-fluorodeoxyglucose positron emission tomography (FDG PET) allows the identification of 24–40% of otherwise unrecognised primary tumours. To our knowledge, the studies on this topic have been conducted using 18F-FDG PET imaging alone. The aim of this study was to evaluate the potential additional diagnostic role of fused 18F-FDG PET-CT imaging for the detection of metastatic occult primary tumours.