Immune-checkpoint inhibitors induced diarrhea and colitis: a review of incidence, pathogenesis and management.

Diarrhea and colitis are among the most commonly encountered immune-mediated adverse events among patients receiving antiprogrammed cell death protein/ligand-1 (PD-1/L1) as well as anticytotoxic T-lymphocyte-associated protein 4 (CTLA-4) antibodies. With growing indications and widespread use of immune checkpoint inhibitors, it is imperative to summarize the current body of evidence concerning the incidence, pathogenesis, risk factors, diagnostic challenges, and treatment options currently available for the management of immune-mediated diarrhea and colitis. Additionally, with emerging evidence analyzing the resumption of immune checkpoint inhibitors, it is pivotal to summarize our current understanding and future challenges.Immune-mediated diarrhea and colitis can potentially be a viable surrogate marker for improved survival as it is validated further in large-scale studies. Early endoscopic evaluation can aid in the identification of patients at risk of developing steroid refractory immune-mediated colitis, and hence can be chosen to receive early add-on therapy with infliximab, vedolizumab or fecal microbiota transplantation, an emerging treatment option for immune-mediated diarrhea and colitis. Resuming immune checkpoint inhibitors carries a manageable risk of recurrent diarrhea and colitis, with most cases being mild and effectively managed with immunosuppressive therapy.As our understanding of immune-mediated diarrhea and colitis grows, it is likely that this clinicopathologic entity will represent more than just an adverse event. With a growing number of treatment options, the management algorithms for immune-mediated diarrhea/colitis are likely to evolve in the future.