Diagnostic Value of FDG PET/CT in Differentiation of autoimmune pancreatitis from pancreatic cancer

Objectives FDG-PET/CT has been widely used for the diagnosis of autoimmune pancreatitis (AIP). Because autoimmune pancreatitis is easily misdiagnosed as pancreatic cancer (PC), we attempted to clarify the differences in FDG-PET findings between AIP and PC.

Methods We compared FDG-PET/CT findings between 26 patients with AIP (including 22 dual-phase scans) and 40 patients with PC (including 34 dual-phase scans). The findings of pancreatic and extra-pancreatic lesions were evaluated visually or semiquantitatively using the maximum standardized uptake value (SUVmax) and the accumulation pattern of FDG.

Results FDG uptake was found in all 26 patients with autoimmune pancreatitis, whereas it was found in 35 of 40 patients (87.5%) with pancreatic cancer. An accumulation pattern characterized by focal lesion was significantly more frequent in pancreatic cancer (82.5%, 33/40), whereas a longitudinal shape indicated AIP (69.2%, 18/22). The SUVmax of pancreatic lesions or lesions/liver was significantly different between AIP and PC in both the early and delayed phase (P all<0.05). Areas of ROC curve were 0.713(early SUVmax), 0.713(delayed SUVmax), 0.713(early lesions/liver SUVmax), and 0.748(delayed lesions/liver SUVmax). Changes of bile were found in 46.15% (12/26) patients with AIP, whereas it was found in 15.0% (6/40) patients with PC. There were no significant difference in SUVmax or frequent of the mediastinal and retroperitoneal lymph node in patients with AIP and PC (P all>0.05).SUVmax of the salivary gland and prostate were significantly higher in patients with AIP than in those with PC (P all<0.05). In male patients，inverted “V” shaped FDG uptake in the prostate was significantly more frequent in patients with autoimmune pancreatitis(56.00%，14/25) than in those with pancreatic cancer (11.42%, 4/35).

Conclusions By manifesting some metabolic characteristics of pancreatic and extra-pancreatic lesions, FDG-PET is useful to differentiate autoimmune pancreatitis from pancreatic cancer.

Research Support This study is funded by National Natural Science Foundation of China ((81170435,81471714)); China Postdoctoral Science Foundation (20100480545);The International Cooperationprojects ofShanghai Science and Technology Committee (10410708800).