The efficacy of FDG-PET/CT for the differentiation of autoimmune pancreatitis from pancreatic cancer

Objectives Autoimmune pancreatitis (AIP) is a unique subtype of chronic pancreatitis, which is sometimes misdiagnosed as pancreatic cancer. The purpose of this study was to investigate the FDG-PET/CT findings in patients with AIP and to evaluate the efficacy of FDG-PET/CT for the differentiation of AIP from pancreatic cancer.

Methods Twenty-nine patients (22 males, 7 females; median age, 67 years) with AIP and 33 (20 males, 13 females, median age, 69 years) with pancreatic cancer were enrolled in this study. FDG-PET/CT was performed for both disease groups of patients prior to any treatments. All of the patients with AIP in our study met the diagnostic criteria for AIP proposed by the Japanese Pancreas Society. And all the patients with pancreatic cancer enrolled in this study were histopathologically diagnosed by biopsies or surgeries. FDG accumulation and accumulation pattern in the pancreatic lesion, and extrapancreatic FDG uptake were retrospectively evaluated visually and semiquatively using maximum standardized uptake value (SUVmax).

Results The average±SD of SUVmax in AIP and pancreatic cancer lesions were 6.04 ±2.02 and 7.48 ±4.00, respectively. No significant difference was observed in FDG accumulation between AIP and pancreatic cancer (p=0.08). Twenty-six (89.7%) of 29 AIP patients presented FDG accumulation in more than one pancreatic regions (head, body, or tail), whereas 22 (66.7%) of 33 pancreatic cancer patients showed FDG accumulation in only one pancreatic region (p<0.01). Heterogeneous FDG accumulation was found in 33 (79.3%) of AIP patients, though 23 (69.7%) pancreatic cancer patients showed focal FDG accumulation (p<0.01). FDG uptake by the hilar or mediastinal lymph node was significantly more frequent in AIP (26 cases) than in pancreatic cancer (10 cases).

Conclusions Although the intensity of FDG accumulation in pancreatic lesion may not useful, accumulation pattern and extrapancreatic involvement should be considered for the differentiation between AIP and pancreatic cancer