Immune Checkpoint Inhibitor-Induced Colitis: How Long Does the Threat Last?

Delayed immune-related events (DIRE) occur after ≥90 days of discontinuation of immunotherapy. Pembrolizumab is a monoclonal antibody that targets the programmed cell death protein 1 (PD-1) receptor of lymphocytes and is used frequently in the management of multiple cancers. Immunotherapy-related adverse events (irAE) are common; most occur six to seven weeks after starting immunotherapy. However, DIRE could also arise months after the stopping therapy. Although many cases of immunotherapy-induced colitis have been reported, data on colitis DIRE is limited. We present the case of a 76-year-old gentleman with bladder cancer who received pembrolizumab and developed significant diarrhea after four months of discontinuation of immunotherapy. His workup included a sigmoidoscopy with a biopsy showing evidence of immune-related colitis. In addition, the patient received steroids achieving complete resolution of diarrhea.