¹⁸F-FDG PET/CT in the assessment of carcinoma of unknown primary origin

Abstract

Purpose.

Metastatic cancers of unknown primary origin are characterised by a poor prognosis, with a survival rate from diagnosis of approximately 12 months. Conventional radiological imaging allows detection of 20%–27% of primary cancers, whereas the detection rate with positron emission tomography (PET) is 24%–40%. The aim of this study was to assess the role of ¹⁸F-fluorodeoxyglucose (FDG) PET/computed tomography (CT) in the identification of occult primary cancers.

Materials and methods.

The study population consisted of 38 consecutive patients with histologically proven metastatic disease and negative or nonconclusive conventional diagnostic procedures. All patients were studied by ¹⁸F-FDG PET performed according to the standard procedure (6 h of fasting, intravenous injection of 370 MBq ¹⁸F-FDG, and image acquisition with a PET/CT scanner for 4 min per bed position).

Results.

¹⁸F-FDG-PET/CT detected the occult primary cancer in 20 cases (53%), showing higher sensitivity than that reported for any other imaging modality, including PET.

Conclusions.

The encouraging results, if validated by larger series, support the use of PET/CT in patients with carcinoma of unknown primary origin and negative conventional imaging results.