Two cases of immune checkpoint inhibitor-associated colitis with contrasting outcomes

With the widespread use of immune checkpoint inhibitors (ICIs) to treat cancer, immune-related adverse events (irAEs) have become a topic of research. Gastrointestinal disorders, such as diarrhea and colitis, are frequently occurring irAEs, particularly grade 3-5 irAEs. Here, we report two cases of ICI-associated colitis with contrasting outcomes. Colonoscopy findings of colitis due to ICI are erythema, luminal bleeding, erosions, and ulcerations, which are nonspecific findings. Biopsy is necessary for a definitive diagnosis. Both cases showed CD8+ lymphocyte infiltration, leading to the definitive diagnosis. Early diagnosis and intervention for ICI-associated colitis improve the prognosis, and colonoscopy and mucosal biopsy should be performed promptly when ICI-associated colitis is suspected.