The Clinical Value of Dual-Time Point 18F-FDG PET/CT for Differentiating Extrahepatic Cholangiocarcinoma From Benign Disease

Purpose: The aim of this study was to assess the value of dual-time point PET/CT in the differentiation of extrahepatic cholangiocarcinoma from benign stricture and the added benefits of delayed PET/CT image. Patients and Methods: Thirty-nine patients with suspected extrahepatic biliary malignancy based on conventional imaging studies such as ultrasonography, CT, and MRI between July 2008 and December 2010 were included. All patients underwent dual-time point PET/CT scans at 1 and 2 hours after radiotracer injection. From the site of suspected malignancy, the SUVmax for both time points (SUVmax1 and SUVmax2), the percent change in SUVmax between the 2 (Delta SUVmax) and the ratio of SUVmax1, SUVmax2, Delta%SUVmax in comparison with average SUV of right hepatic lobe (T/L ratio1, T/L ratio2, and Delta%T/L ratio) were generated. Diagnostic performances using visual assessment and various SUVmax cutoff values were analyzed in the differential diagnosis of extrahepatic cholangiocarcinoma from benign disease. PET/CT results were correlated with histological results and radiological follow-up for at least 6 months. Results: Of 39 patients, the final diagnosis was cholangiocarcinoma in 34 and benign disease in 5. Between malignant and benign lesions, there were significant differences in SUVmax1 (5.43 +/- 4.66 vs 2.26 +/- 0.83, P = 0.003) and SUVmax2 (6.02 +/- 5.26 vs 2.26 +/- 0.76, P = 0.002). There was no significant difference in Delta%SUVmax, T/L ratio1, T/L ratio2, and Delta%T/L ratio. On receiver operator curve analysis, SUVmax1 with cutoff value of 2.5 demonstrated sensitivity of 97.6%, specificity of 60.0%, and accuracy of 92.3% and SUVmax2 with cutoff value of 3.1 demonstrated sensitivity of 88.2%, specificity of 100%, and accuracy of 89.7%. Conclusion: SUVmax from both early and delayed PET/CT scans are useful parameters in the differentiation of extrahepatic biliary malignancy from benign disease. However, there was no added benefit of delayed PET/CT in patients suspicious for extrahepatic cholangiocarcinoma.