Rare Occurrence of Immunotherapy-Related Gastritis and Duodenitis in a Single Tertiary Medical Center: A Diagnostic Challenge

Introduction Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment. While generally well-tolerated, some immune-related adverse events (ir-AEs) can impact patient care, highlighting the need for accurate diagnosis. Immunotherapy-related gastritis and duodenitis (ir-GD) are two rare ir-AEs. Due to their low incidence and non-specific symptoms, standardized diagnostic criteria and evidence-based treatment guidelines are lacking. Methods We conducted a retrospective analysis of patients undergoing esophagogastroduodenoscopy (EGD) while receiving ICI. Our diagnostic criteria for ir-GD required at least two of three gastritis or duodenitis (GD) criteria (symptoms, EGD findings, or microscopic findings) along with at least one ICI-related criterion. Patients with ir-GD were compared to those without ir-GD. Results Of 2,553 patients treated with ICI between 2017 and 2023, 62 (2.4%) underwent EGD, of whom nine (0.4%) met the ir-GD diagnostic criteria. Nine other patients (0.4%) had GD unrelated to ICI. Notably, three of the nine patients (33%) with ir-GD had pre-existing inflammatory gastrointestinal conditions, compared to two of 53 patients (4%) in the non-ir-GD cohort (P = 0.019). Patients with ir-GD were significantly more symptomatic (100% vs 58%, P = 0.009). However, no single symptom was specific to ir-GD. While eight of nine (89%) patients with ir-GD were treated with proton pump inhibitors, only three (33%) required corticosteroids. Symptom resolution occurred in all patients, and three patients successfully underwent re-challenge. Conclusion ir-GD is a rare ir-AE that can be challenging to distinguish from GD caused by other etiologies. Once diagnosed, clinicians may consider non-steroidal treatment approaches in mild cases and, in selected cases, even ICI re-challenge.