Immune-Related Adverse Events of the Gastrointestinal System

SIMPLE SUMMARY: Immunotherapy is an effective cancer treatment that activates the immune system to target and destroy cancer cells. The emerging use of a form of immunotherapy referred to as immune checkpoint inhibitors is often limited by the development of immune-related adverse events. This often leads to the discontinuation of treatment and limits good outcomes. In this review, we summarize the spectrum of immune-related adverse events of the gastrointestinal system with a focus on their management and emerging therapies. ABSTRACT: Immune checkpoint inhibitors (ICI) are a form of immunotherapy that have revolutionized the treatment of a number of cancers. Specifically, they are antibodies targeted against established and emerging immune checkpoints, such as cytotoxic T-cell antigen 4 (CTLA4), programmed cell death ligand 1 (PD-L1) and programmed cell death 1 protein (PD-1) on CD8-positive T cells, which promote the destruction of tumor cells. While the immune checkpoint inhibitors are very effective in the treatment of a number of cancers, their use is limited by serious and in some cases life-threatening immune-related adverse events. While these involve many organs, one of the most prevalent serious adverse events is immune checkpoint inhibitor colitis, occurring in a significant proportion of patients treated with this therapy. In this review, we aim to broadly describe the immune-related adverse events known to occur within the gastrointestinal system and the potential role played by the intestinal microbiome.