Checkpoint inhibitor colitis: a gastroenterologists’ perspective

Immune checkpoint inhibitor (ICI) medications are increasingly widely used for the treatment of certain forms of cancer. Although they offer significant prognostic benefits, they are associated with a broad spectrum of immune-related adverse effects (irAEs). Checkpoint inhibitor colitis (CIC) is considered the most severe and is the most common cause for discontinuation of ICI. The risk of CIC varies by mechanism of action of the ICI in question and whether combination immunotherapy is used. CIC is diagnosed endoscopically, including histology. Differential diagnoses include infections, cytomegalovirus and other irAEs such as thyroiditis, coeliac disease and enteritis. Initial management includes temporary cessation of the ICI and the administration of corticosteroid use with escalation to biological medications for corticosteroid refractory cases. Both infliximab and vedolizumab have demonstrated efficacy in excess of 80% of such cases following three infusions. In selected cases, re-challenge with ICI can be attempted with similar rates of CIC to patients without prior CIC. Patients with inflammatory bowel disease have a significant risk of exacerbation if treated with ICI. Despite this, considering the prognostic benefit from treatment with ICI, expert consensus does not contraindicate ICI use in patients with pre-existing inflammatory bowel disease.