D0017 - Distinct Imaging Patterns of Immune Checkpoint Inhibitor-Induced Acute Pancreatitis

Introduction: The presentation of immune checkpoint inhibitor (ICI)-induced pancreatic injury ranges from asymptomatic hyperlipasemia to acute pancreatitis. Imaging features of ICI-induced acute pancreatitis (ICI-AP) remain poorly described. We evaluated radiographic patterns of pancreatic inflammation in patients with ICI-AP.

Methods: We assessed a retrospective cohort of patients diagnosed with ICI-AP after initiation of ICI therapy between 2011 and 2019. Abdominal imaging findings with computed tomography (CT), magnetic resonance imaging (MRI), and 18-Fluorine-flurodeoxyglucose positron emission tomography (¹⁸F-FDG PET/CT) were reviewed by an independent radiologist. We performed univariate analyses to evaluate associations between clinical characteristics and radiographic patterns of ICI-AP.

Results: Among 6,450 cancer patients treated with ICI, 27 (0.4%) developed ICI-AP. All three Atlanta criteria for AP (typical symptoms, imaging, and lipase ≥3 upper limit of normal) were satisfied in 13 (48%). Abdominal pain was present in 23 (85%), and 4 (15%) presented asymptomatically with hyperlipasemia and pancreatic inflammation on imaging. Diagnostic abdominal imaging was performed in 26/27 patients (mean age 62.4 ± 11.3 years, 46% female, 92% White) via CT in 22 (85%), MRI in 3 (12%), and ¹⁸F-FDG PET/CT in 1 (4%). The most frequent radiologic appearance was a diffuse interstitial pattern with diffuse edematous pancreas and peripancreatic stranding, present in 10 (38%) patients, followed by a focal interstitial pattern with focal pancreatic edema and peripancreatic stranding in 7 (26%), and pancreatic enlargement without peripancreatic inflammation in 3 (12%). Six patients (23%) had normal imaging. Individuals with diffuse interstitial inflammation and normal imaging were more likely to be female (p=0.02). Those with diffuse inflammation or pancreatic enlargement without inflammation were older than those with focal inflammation and normal pancreatic imaging (p=0.046).

Discussion: We propose three distinct radiologic patterns of ICI-AP. The notable subset of patients who were asymptomatic but had imaging evidence of ICI-AP supports the role of abdominal imaging in patients on ICIs with hyperlipasemia. The presence of pancreatic enlargement without peripancreatic inflammation in a small but notable proportion of patients highlights the importance of comparing baseline pancreatic imaging when interpreting imaging for ICI-AP.