Whole Body 18F-FDG PET/CT Imaging in the Detection of Primary Tumours in Patients with a Metastatic Carcinoma of Unknown Origin

Purpose: The aim of this study was to evaluate the role of whole body 18F-FDG PET/CT imaging in thedetection of primary tumors in patients with a metastatic cancer from an unknown primary site. Methods: Thestudy population consisted of 43 patients with a biopsy proven metastatic disease, negative conventional diagnosticprocedures (including CT/MRI/endoscopic procedures) and a whole body 18F-FDG PET/CT examination.Patients’ records were retrospectively analyzed. According to the final pathologic diagnoses, rate of detection ofthe primary tumor site was determined. Additionally, overall patient survival was calculated to evaluate theprognostic value of 18F-FDG PET/CT findings. Results: A primary tumor site was shown by 18F-FDG PET/CTin 24 patients (24/43; 55.8%). In 18 patients 18F-FDG PET/CT scans were negative (18/43; 41.8%). In a patientwith an adenocarcinoma metastasis 18F-FDG PET/CT was falsely positive for an inflammatory lesion in thelung. Among the 18F-FDG PET/CT positive and negative groups median overall survival was not significantlydifferent (log-rank p=0.573). Conclusion: Whole body 18F-FDG PET/CT imaging has a high rate of detectionof a primary tumor in patients with a carcinoma of unknown origin.