LAUSR

Abstract Introduction: Immune checkpoint inhibitors (ICIs) may lead to immune-related adverse events (irAEs), including the rare complication of immune-related acute pancreatitis (irAP). Current knowledge about irAP is limited to case reports and retrospective studies. Case Presentations: We retrospectively reviewed 8 patients diagnosed with irAP at a high-volume tertiary cancer centre in Chile between 2021 and 2025. Data were collected on cancer type, immunotherapy regimen, symptoms, enzyme levels, imaging, and treatment. The irAP diagnosis was established according to the American Gastroenterological Association criteria. Adverse reactions were graded using CTCAE v5.0. Of the 8 included patients, 4 had melanoma, 2 had breast cancer, and 2 prostate cancer. Seven received PD-1/CTLA-4 combination therapy, and 1 received anti-PD-1 monotherapy. The median time to the irAP diagnosis was 5 months. Seven patients presented with gastrointestinal symptoms. Enzyme elevations and imaging findings were variable. All patients were treated with systemic corticosteroids, and 3 required hospitalisation. Four patients were rechallenged with ICIs. Other grade ≥2 irAEs were observed in 6 patients. No deaths were directly attributable to irAP. Conclusion: As demonstrated, these manifestations can diverge substantially from those of classical pancreatitis, so establishing an irAP diagnosis requires a comprehensive assessment. Corticosteroids are an effective treatment in most cases, and ICI rechallenge may be feasible in selected patients. This case series adds 8 new reports to the limited literature on irAP, underscoring its clinical heterogeneity and the need for tailored management. Further research and detailed case reporting are essential to improve diagnosis and treatment of this rare toxicity.