The role of FDG PET/CT imaging in patients with unknown primary tumours

Unknown primary tumour (UPT) refers to the presence of metastatic disease for which the site of the primary lesion remains unidentified after conventional diagnostic procedures. Prognosis can be changed significantly after detection of the primary lesion. The aim of this retrospective study was to evaluate the performance of F-18 Fluorodeoxy-glucose (FDG) positron emission tomography (PET)/computarize tomogpaphy (CT) in the identification of primary lesion in patients with unknown primary tumour who had negative diagnostic resultsIn this study, between January 2006-Agust 2009 sixty-one patients with UPT were with conventional imaging modalities analyzed. Twenty-three patients were females and thirty-eight of them were males; age range 24?90, mean age 60.5±15.5 years old. Seventeen patients had presented with cervical metastases and forty-four patients with extracervical metastasis. The patients were injected 370 MBq of F-18 FDG intravenously and were imaged using PET/CT camera. The images were evaluated both visually and semiquantitatively using standardized uptake value (SUVThirty-five (57.3%) patients showed pathologic FDG accumulations might be related to primary tumour sites. PET/CT results were true positive in twenty-one cases. Among these 10 lung ca, 4 pancreas ca, 2 nasopharynx ca, 1 tonsil ca, 1 prostat ca, 1 breast ca, 1 colon ca and 1 endometrium ca vere detected. Detection rate, sensitivity and specificity of PET/CT were 34.4%, 72.4% and 56.2%, respectively. In detection rate of UPT no difference was found between presence of cervical and extracervical metastases, adenocarcinoma and carcinoma metastases. PET/CT showed additional metastatic lesions in 22 (36%) patients and changed staging and therapy planning in 33 (54In conclusion, FDG PET/CT is a valuable diagnostic tool in patients with UPT. It could help detecting primary and selecting the appropriate treatment protocols. Also, FDG PET/CT can reveal unknown additional metastases and thus influence therapy selection. FDG PET/CT should be accepted as a first-line diagnostic tool for these patients who had poor prognosis.