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Q J Nucl Med Mol Imaging. 2006 Mar;50(1):15-22.

Role of whole body positron emission tomography/computed tomography scan with 18F-fluorodeoxyglucose in patients with biopsy proven tumor metastases from unknown primary site.

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University Nuclear Medicine Service, ASO S. Giovanni Battista, Turin, Italy.



The aim of this study was to evaluate the role of whole body PET/CT scan with (18)F-fluorodeoxyglucose (FDG) in the detection of the primary tumor in patients with metastatic cancer from unknown primary origin (CUP syndrome).


Sixty-eight consecutive patients, with CUP syndrome (39 lymph nodes, 29 visceral biopsy proven tumor metastases), underwent a whole-body FDG-PET/CT study. All enrolled patients were unsuccessfully studied, within the previous month, with physical examination, laboratory tests and conventional diagnostic procedures. All the pathological findings identified at PET/CT scan and suspected for primaries, were further investigated. After PET study, the minimum follow-up period for the inclusion in the studied population was 3 months.


The primary tumor site was correctly identified by FDG-PET/CT in 24 patients (24/68, 35.3%): lung (n=9), rino/oro-pharynx (n=6), pancreas (n=5), colon (n=2), uterus (n=2). In 5 cases, FDG-PET scan did not identify a primary pathological focus, which was subsequently detected by other diagnostic methods within 3 months. In 39 patients (39/68, 57.4%), the primary tumor site was not localized. However, in 9 of them, FDG-PET/CT scan identified further unexpected metastases, modifying the stage of disease. Overall, the following oncological treatment was influenced by the PET scan, in a total of 33 patients (33/68, 48.5%).


Our data strongly support the diagnostic contribution of whole body FDG-PET/CT scan in the evaluation of patients with CUP syndrome and suggest its use in an early phase of the diagnostic iter to optimize patient management.

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