S65 Distinct Imaging Patterns of Immune Checkpoint Inhibitor-Induced Acute Pancreatitis

Abstract

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). Conclusion: 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. (Table) Table 1. - Title: Imaging Characteristics in Patients with Immune Checkpoint Inhibitor-Induced Acute Pancreatitis Characteristics Overall (N = 26) Diffuse interstitial pattern (N = 10) Focal interstitial pattern (N = 7) Pancreatic enlargement alone (N = 3) Normal (N = 6) P-value Age (years), mean (SD) 62.4 (11.3) 65.6 (11.9) 57.4 (14.6) 70.0 (3.6) 59.2 (4.0) 0.046 Female, n (%) 12 (46.2%) 6 (60.0%) 1 (14.3%) - 5 (83.3%) 0.02 Race (White) n (%) 24 (92.3%) 9 (90.0%) 7 (100%) 2 (66.7%) 6 (100%) 0.27 Cancer type, n (%) 0.40 Melanoma 11 (42.3%) 3 (30.0%) 2 (28.6%) 2 (66.7%) 4 (66.7%) Non-melanoma 15 (57.8%) 7 (70.0%) 5 (71.4%) 1 (33.3%) 2 (33.3%) ICI class, n (%) 0.77 CTLA4 2 (7.7%) - 1 (14.3%) - 1 (16.7%) PD1/PDL1 18 (69.2%) 8 (80.0%) 5 (71.4%) 2 (66.7%) 3 (50.0%) CTLA4 + PD1/PDL1 6 (23.1%) 2 (20.0%) 1 (14.3%) 1 (33.3%) 2 (33.3%) Pancreatitis severity by revised Atlanta criteria, n (%) 0.38 Mild 23 (88.5%) 9 (90.0%) 7 (100%) 3 (100%) 4 (66.7%) Moderately severe 3 (11.5%) 1 (10.0%) - - 2 (33.3%) Lipase severity by CTCAE v.5 0.99 3 4 (15.4%) 2 (20.0%) 1 (14.3%) - 1 (16.7%) 4 22 (84.6%) 8 (80.0%) 6 (85.7%) 3 (100%) 5 (83.3%) Days from ICI initiation to pancreatitis, mean (SD) 161.8 (242.5) 134.0 (148.7) 156.1 (158.8) 451.0 (633.4) 70.2 (40.7) 0.52 Duration of lipase elevation (days), mean (SD) 65.4 (81.1) 54.2 (62.3) 41.0 (37.0) 32.3 (43.4) 129.0 (130.0) 0.66 Managed with steroids, n (%) 21 (80.1%) 8 (80.0%) 5 (71.4%) 2 (66.7%) 6 (100%) 0.53 ICI discontinued due to ICI-induced pancreatic injury, n (%) 19 (73.1%) 7 (70.0%) 5 (71.4%) 1 (33.3%) 6 (100%) 0.23 Response to steroids, n (%) 10 (38.5%) 3 (30.0%) 4 (57.1%) 1 (33.3%) 2 (33.3%) 0.76 Abbreviations: Common Terminology Criteria for Adverse Events version 5.0 (CTCAE v.5); cytotoxic T-lymphocyte-antigen protein-4 (CTLA-4); Immune checkpoint inhibitor (ICI); programmed cell death-1 (PD-1) / PD-1 ligand (PD-L1).