Severe luminal stricture in immune-related adverse event-associated enteritis: a case report.

Immune checkpoint inhibitors, such as ipilimumab and nivolumab, target cytotoxic T-lymphocyte-associated antigen 4 and programmed cell death protein 1, respectively, and are increasingly used in cancer treatment. These therapies can induce immune-related adverse events, including colitis and ileitis. However, the reports on enteritis caused by these immune-related adverse events are limited, particularly in Japan, with only a few case reports available. The incidence, typical location, and timing of onset of such inflammation remain undefined. We present the case of a 56-year-old male patient who developed severe colitis and enteritis after receiving immune checkpoint inhibitor treatment for metastatic lung tumor recurrence following surgery for renal cell carcinoma. Despite treatment with high-dose prednisolone and infliximab, the patient developed colonic perforation, requiring subtotal proctocolectomy and colostomy. Six months postoperatively, he presented with enteritis with luminal narrowing. Oral budesonide was initiated, and endoscopic balloon dilation of the stenotic site improved the obstruction. Consequently, 3.5 years after initiating immune checkpoint inhibitor therapy, the metastatic lung tumor has not recurred. Moreover, the patient is alive, with no difficulty in oral intake. This report has highlighted the need for careful consideration of immune checkpoint inhibitor administration, even when transitioning to single-agent therapy.