# Rare occurrence of immunotherapy-related gastritis and duodenitis in a single tertiary medical center: a diagnostic challenge

## TL;DR

This study examines the rare but challenging condition of immunotherapy-related gastritis and duodenitis, highlighting its diagnostic difficulties and treatment outcomes.

## Contribution

The study introduces specific diagnostic criteria for immunotherapy-related gastritis and duodenitis and reports on its clinical features and management.

## Key findings

- Only 0.4% of patients treated with immune checkpoint inhibitors met the criteria for immunotherapy-related gastritis and duodenitis.
- Patients with immunotherapy-related gastritis and duodenitis were more likely to have preexisting inflammatory gastrointestinal conditions.
- Most patients with immunotherapy-related gastritis and duodenitis improved with nonsteroidal treatments, and some successfully underwent rechallenge with immunotherapy.

## Abstract

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) is a rare ir-AE. Due to its low incidence and nonspecific symptoms, standardized diagnostic criteria and evidence-based treatment guidelines are lacking.

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.

Of 2553 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 preexisting inflammatory gastrointestinal conditions, compared to two of 53 patients (4%) in the non-ir-GD cohort (P = .019). Patients with ir-GD were significantly more symptomatic (100% vs 58%, P = .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 rechallenge.

ir-GD is a rare ir-AE that can be challenging to distinguish from GD caused by other etiologies. Once diagnosed, clinicians may consider nonsteroidal treatment approaches in mild cases and, in selected cases, even ICI rechallenge.