Ileostomy for Refractory Immune Checkpoint Inhibitor-Associated Colitis: A Case Report and Literature Review

Immune checkpoint inhibitors (ICIs) are widely used to treat malignant tumors and have transformed cancer treatment; however, immune-related adverse events (irAEs) can occur due to excessive immune responses. Among these, immune checkpoint inhibitor-related colitis (irAE colitis) presents with symptoms resembling ulcerative colitis, for which high-dose corticosteroids and anti-TNF-alpha antibodies are recommended. Surgical treatment has not been well established for cases refractory to medical therapy. We report a case of a 64-year-old male patient with PD-L1-positive recurrent lung adenocarcinoma who developed hematochezia and diarrhea eight weeks after initiating pembrolizumab, leading to a diagnosis of irAE colitis. Despite treatment with corticosteroids, infliximab, mesalazine, and leukocytapheresis, the colitis remained refractory. Due to the patient's poor performance status, proctocolectomy and subtotal colectomy were not indicated, and a diverting loop ileostomy was performed to rest the colon. Following surgery, abdominal symptoms resolved, allowing chemotherapy to resume three months later. Stoma closure was not possible due to persistent mucosal lesions on colonoscopy, but no symptoms of colitis were observed, and nivolumab was administered from the 18^th month post surgery. However, the treatment was ineffective, and the patient succumbed to the primary disease two years after surgery. This case highlights the potential role of diverting loop ileostomy in managing refractory irAE colitis, though further discussion is needed regarding surgical strategies and the feasibility of resuming ICIs following colitis development.