Remission of ulcerative colitis flare-up induced by nivolumab

Background Immune checkpoint inhibitors (ICIs) have been used to treat many cancers, but ICIs are rarely administered for malignant tumours coexisting with inflammatory bowel disease. Methods and results We report a 77-year-old man experiencing an ulcerative colitis (UC) flare-up after receiving nivolumab as third-line therapy for multiple metastases of renal cell carcinoma. Mild UC (proctitis form) had been diagnosed at age 59 years and remission was maintained for 17 years with only a low dose of 5-ASA. After nivolumab treatment, the patient developed diarrhoea, bloody stools and was hospitalised. Computed tomography revealed inflammation involving the entire colon and endoscopy revealed severe UC exacerbation. Histological analysis showed UC findings and also increased crypt apoptosis which is unusual for inflammatory bowel diseases, while being typical of ICI-induced colitis. As with ICI-induced colitis, this exacerbation was strongly suggested to have been caused by nivolumab, although remission was achieved by increasing the 5-ASA dose to 4000 mg without prednisolone. Conclusion The administration of ICI for UC is not as yet sufficiently safe and further research is required.