Characteristics of Immune Checkpoint Inhibitor-Induced Colitis: A Systematic Review

Immune checkpoint inhibitors (ICIs) including anti-CTLA-4, anti-PD-1, and anti-PD-L1 antibodies have been increasingly used for various malignancies. These ICIs activate immune functions to treat malignant tumors; however, this causes characteristic complications called immune-related adverse events (irAE). In the gastrointestinal tract, ICIs cause adverse events such as diarrhea and enterocolitis, thus warranting treatment discontinuation. These irAEs require treatment that suppresses immunity; however, no treatment strategies based on approved guidelines have been reported. This review aimed to investigate the current treatment status for refractory cases of ICI-induced colitis in accordance with their diagnosis, therapy, and prognosis.

We systematically reviewed studies in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) checklist. Two investigators searched PubMed and Scopus in January 2019. We extracted data, including the number of ICI-treated patients developing colitis and diarrhea. The number of cases classified as severe per the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE) definitions and the progress of corticosteroid-treated and anti-TNF-α- antibody-treated cases (e.g., infliximab) were recorded. Details of further treatment were also recorded for cases that did not improve with antiTNF-α- antibody. Among patients receiving anti-CTLA-4 antibody, corticosteroids were administered to 14.6% of patients, and infliximab was administered to 5.7% of patients. Among patients receiving anti-PD-1/PD-L1 antibody, corticosteroids were administered to 2.37% of patients. For refractory cases unsuccessful with infliximab, the continuation of infliximab every 2 weeks, tacrolimus administration, prolonged corticosteroid treatment, colectomy, or vedolizumab administration were reported.

Treatment of ICI-induced colitis is important to avoid the need to discontinue cancer treatment. Many therapeutic agents for inflammatory bowel disease are reportedly effective in treating refractory ICI-induced colitis.