Abstracts
2001 Digestive Disease Week

# 2465 Diagnostic Value of Positron Emission Tomography Using 18F-fluorodeoxyglucose and 11C-aceate for the Differentiation of Chronic Pancreatitis and Pancreatic Adenocarcinoma.
Ib Rasmussen, Jens Sorensen, PET center, Ulf Haglund, Uppsala, Sweden

BACKGROUBD: In some patients it is impossible to differentiate between mass forming chronic pancreatitis and adenocarcinoma of the head of the pancreas using standard anatomical imaging. Positron emission tomography using 2-[¹⁸F]fluoro-2deoxy-D-glucose (¹⁸FDG-PET) and 1-[¹¹C]-acetate (¹¹C-acetate-PET) are methods taking advantage of the metabolic differences in benign and malignant tissues. ¹⁸FDG-PET has been proposed to provide high sensitivity and diagnostic accuracy in the differentiation between malignant and benign pancreatic masses whereas the usefulness of ¹¹C-acetate-PET alone or in combination with ¹⁸FDG-PET has not been determined. Objective: To assess the ability ¹⁸FDG-PET and ¹¹C-acetate-PET to differentiate chronic pancreatitis from pancreatic adenocarcinoma in patients presenting with a pancreatic mass.

METHODS: 20 patients (12 M, 8 F; mean age ±SD 59.7±11 yrs, range 38-77 yrs) with a pancreatic mass of unclear etiology were prospectively included. All patients underwent ¹⁸FDG-PET and 18 of them ¹¹C-acetate-PET. The scans were evaluated qualitatively and quantitatively; the later using calculated regional standardized uptake value (SUV). Receiver operating characteristic (ROC) curve analysis was used for evaluation of the results Final diagnosis was established using histopathologic evaluation of resected specimen, biopsy, and in 2 patients clinical follow-up.

RESULTS: The final diagnosis was adenocarcinoma of the pancreas in 12 patients (60%) and chronic pancreatitis in 8. Qualitative evaluation of ¹⁸FDG-PET imaging revealed 3 false-negative and 1 false-positive results. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were 75%, 88%, 90%, 70%, and 80%, respectively. The cut-off SUV to differentiate malignant from benign disease was calculated to be 3.6 demonstrating a sensitivity of 91,7% and a specificity of 75%. There was no significant difference between the qualitative and quantitative results ¹¹C-acetate-PET did not improve the overall results.

CONCLUSIONS: We could not confirm previous reports of high sensitivity and diagnostic accuracy of ¹⁸FDG-PET imaging for differentiating adenocarcinoma of the pancreas from chronic pancreatitis in patients presenting with a pancreatic mass. No additional diagnostic benefit could be demonstrated using ¹¹C-acetate-PET.