Differentiation between Malignant and Benign Solitary Lesions in the Liver with (18)FDG PET/CT: Accuracy of Age-related Diagnostic Standard

Objective: This study was to determine the reliability of age-stratified diagnostic index in differential diagnosis of malignant and benign solitary lesions in the liver using fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography ((18)FDG PET/CT). Methods: The enrolled 272 patients with solitary lesions in the liver were divided into three age groups, younger group (under 50 years), middle-aged group (50-69 years), and elderly group (70 years and above). Patients' ages were compared, and the optimal cut-offs of the standard uptake value (SUV) ratio (tumor-to-non-tumor ratio of the SUV), as well as areas under the curves (AUC), were evaluated in terms of malignant and benign lesions in each age group by using receiver operating characteristic (ROC) analysis. Based on optimal cut-offs, the sensitivity, specificity, accuracy were calculated, and the diagnostic accordance rate was compared between each age group and all patients, supported by (18)FDG PET/CT imaging data. Results: There was a significant age difference between the malignant and benign groups (t=3.905 p=0.0001). ROC analysis showed that the optimal cut-off value in all patients, younger group, middle-aged group and elderly group was 1.25, 1.17, 1.45 and 1.25 for SUVratio, and 0.856, 0.962, 0.650, 0.973 for AUC. The chi-square test proved that diagnostic accordance rate of (18)FDG PET/CT in younger group and elderly group were superior to that in all patients (χ(2)=13.352, P=0.0003) and (χ(2)=8.494, P=0.0036). Conversely, overall diagnostic accordance rate in all patient group was higher than that in middle-aged group (χ(2)=9.057, P=0.0026). Representative (18)FDG PET/CT imaging findings are demonstrated. Conclusion: This study indicates that diagnostic optimal cut-offs of SUVratio of liver solitary lesions of (18)FDG PET/CT were different in each age group. In addition, the diagnostic performance of SUVratio was better in younger and elderly groups than that in all patients, and was poorer in middle-aged group than that in all patients. Therefore, age difference appears to be one of the important factors for discriminating malignant liver lesions from benign ones using (18 )FDG PET/CT.