Prediction of survival and evaluation of diagnostic accuracy whole body 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography in the detection carcinoma of unknown primary origin.

PURPOSE: The aim of the current study was to determine the diagnostic accuracy of whole-body 18F-fluoro-2-deoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) in detecting carcinoma of unknown primary (CUP).

MATERIALS AND METHODS: A total of 7,636 patients were investigated by FDG-PET/CT examinations at our Institution. We retrospectively evaluated the file records of 432 patients who were referred to FDG PET/CT imaging with a diagnosis of cancer of unknown primary, and included 316 of the patients with histopathologic verification at the final diagnosis. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated. The Kaplan-Meier test was used for survival analysis. Median survival rate was calculated to evaluate the prognostic value of the FDG-PET/ CT findings.

RESULTS: In the search for a primary, FDG-PET/CT findings correctly diagnosed lesions as the site of the primary true positive in 238 cases, 10 findings diagnosed no site of a primary and none was subsequently proven true negative, 12 diagnoses were false positive and 56 were false negative. The sensitivity of FDG-PET/CT is 81% and the specificity 45%. Positive predictive value, negative predictive value and diagnostic accuracy were 95%, 15% and 78%, respectively.

CONCLUSIONS: Whole-body FDG-PET/CT imaging is proven to be useful method in the search for the primary focus and metastases in patients with cancer of unknown primary.