Imaging findings of immune checkpoint inhibitor associated pancreatitis.

PURPOSE

To describe contrast-enhanced computed tomography (CECT), 18-Fluorine (F)-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT and magnetic resonance imaging (MRI) findings of immune checkpoint inhibitor (ICI) associated pancreatitis in patients undergoing immunotherapy for solid malignant tumours.

METHOD

In this retrospective study, 25 patients with clinical and/or biochemical evidence of pancreatitis who underwent CECT, MRI and F-FDG-PET/CT while being treated with ICIs were included. Imaging features of acute pancreatitis included: pancreatic enlargement, heterogeneous enhancement, peripancreatic stranding, fluid collection, pseudocyst, necrosis, atrophy and calcification. F-FDG PET/CT imaging was reviewed for pattern of abnormally increased pancreatic FDG uptake. ICI-associated pancreatitis diagnosis was based on clinical, imaging and biochemical findings.

RESULTS

Imaging findings of ICI-associated pancreatitis included diffuse (n = 14) or focal (n = 11) pancreatic enlargement; heterogenous enhancement (n = 21); focal (n = 9) or diffuse (n = 15) peripancreatic infiltration on CECT and MRI. A pattern consistent with acute interstitial pancreatitis was present in 20/25 (80 %) patients, and a pattern consistent with autoimmune pancreatitis in 4/25 (16 %). A mixed pattern was present in one patient (4%). No patient developed necrotizing pancreatitis or a pseudocyst. The CT severity index was < 3 in all patients, consistent with mild pancreatitis. Focal pancreatic FDG uptake was noted in 2/3 (66 %) of patients. Acute imaging findings resolved with treatment in all 25 patients. Pancreatic atrophy developed in 11/25 (44 %).

CONCLUSIONS

ICI-associated pancreatitis typically presents as either focal or diffuse acute interstitial pancreatitis. Post-pancreatitis atrophy is common. The ICI-associated pancreatitis cases in our study were mild, managed conservatively and did not result in local acute complications.