Real-World Patterns of Immune-Related Toxicity in Gastrointestinal Cancer Patients Treated with Immunotherapy: A service evaluation

Abstract

Introduction: Immune checkpoint inhibitors (ICIs) have transformed cancer treatment and are now the standard therapy for several gastrointestinal (GI) malignancies. Although they can improve survival, ICIs are associated with immune-related adverse events (irAEs) that may affect multiple organ systems, potentially impacting treatment continuity and quality of life. Gastrointestinal toxicities, including diarrhoea and colitis, are among the most frequently reported adverse effects. As the use of ICIs expands, understanding the incidence and management of irAEs in routine clinical practice is essential. This service evaluation aimed to quantify ICI use in GI cancers at a tertiary cancer centre, determine the proportion of patients who developed irAEs, and describe referral and management patterns. Methodology: A retrospective observational evaluation was conducted at a London-based hospital. Electronic health records were reviewed to identify patients with GI cancers treated with ICIs between October 2023 and October 2025. A subsequent subgroup analysis was performed for patients who developed irAEs. Data collected included irAE presentation, affected organ system, CTCAE grade, referral source, specialist involvement, and management, including hospital admission, treatment, follow-up, and ICI rechallenge. Findings were summarised using descriptive statistics. Results: Fifty patients were included (mean age 62.2 years; 60% male). Tumour types included liver (50%), upper GI adenocarcinoma (44%), oesophageal squamous cell carcinoma (4%), and rectal cancer (2%). Most patients received first-line ICIs (92%) with palliative intent (90%). Overall, 20 patients out of 50 (40%) developed irAEs, most of which were grade 1–2 (90%). The most affected systems were the gastrointestinal tract (31.8%), skin (18.2%), joints (18.2%), and liver (13.6%), with diarrhoea and rash being the most frequent presentations. Most cases were identified during routine clinic review (59%), and 23.8% required hospital admission. Management included corticosteroids or supportive care, with multidisciplinary referral required in 35% of cases. Treatment discontinuation occurred in 22.7% of confirmed irAE events. Conclusions: irAEs were common but largely manageable. These findings emphasise the need for structured monitoring and coordinated multidisciplinary care to support safe ICI delivery in routine practice. Keywords: Immune checkpoint inhibitors (ICIs); Immune-related adverse events (irAEs); Gastrointestinal cancers; Oncology nursing; Toxicity management.