Value of F-18-FDG PET/CT in patients with hepatic metastatic carcinoma of unknown primary

Purpose This retrospective study aimed to investigate the clinical value of -deoxy-2-(F-18)-fluorodeoxyglucose positron emission tomography/computed tomography (F-18-FDG PET/CT) in detecting primary lesions of hepatic metastases. Methods A total of 124 patients with hepatic metastatic carcinoma of unknown primary underwent whole body F-18-FDG PET/CT imaging. According to the final diagnoses for both primary sites and hepatic metastases that were confirmed either histopathologically or by clinical follow up, all patients were divided into 4 groups: a true positive group (TP, 95 cases), a false positive group (FP, 9), a true negative group (TN, 8) and a false negative group (FN, 12). Results The TP rate of primary lesions, detected by F-18-FDG PET/CT, was 76.61%, the FP rate 7.26%, the TN rate 6.45% and the FN rate 9.68%. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of F-18-FDG PET/CT in the detection of primary tumors were 88.78%, 52.94%, 91.35%, 40%, and 83.06%, respectively. Accurate diagnosis groups (TP, TN) showed a significantly higher SUVmax (standard uptake maximum value) level than that in error diagnosis groups (FP, FN). The SUVmax between hepatic metastases and primary lesions had a positive correlation. The primary tumor sites of hepatic metastases were mainly located in the gastrointestinal organs and the lungs. Conclusions Whole body F-18-FDG PET/CT imaging was sensitive for detecting primary sites/lesions with hepatic metastatases of unknown primary, especially when the SUVmax of hepatic metastases were greater than 4.7.