Abstract
BACKGROUND: The use of immune-checkpoint inhibitors in cancer treatment has become increasingly common, resulting in an increase in the incidence of related side effects. Diarrhoea and colitis have been previously documented as gastrointestinal tract-related side effects of immune-checkpoint inhibitors. Although PD-1/PD-L1 inhibitors produce fewer side effects than CTLA-4 inhibitors, diarrhoea and colitis continue to be reported. However, little is known about the endoscopic features associated with PD-1/PD-L1 inhibitors. In this report, we describe three cases of colitis induced by a PD-1 inhibitor nivolumab. These cases showed endoscopic findings characteristic of ulcerative colitis (UC). Treatment was in accordance with UC therapy, which resulted in beneficial outcomes. CASE PRESENTATION: Three patients with lung cancer treated with nivolumab presented with diarrhoea with (case 2) or without haematochezia (cases 1 and 3). Treatment with nivolumab was ceased and colonoscopy was performed, revealing endoscopic features similar to those of UC. These patients were diagnosed with nivolumab-induced colitis. Case 1 was treated with mesalazine, whereas cases 2 and 3 were treated with corticosteroids. Subsequently, their symptoms improved. CONCLUSIONS: Nivolumab-induced colitis exhibited similar characteristics to UC. Treatment was similar to that for UC and was successful.