Immune checkpoint inhibitor-associated colitis in unresectable hepatocellular carcinoma: two cases of early onset after treatment with durvalumab plus tremelimumab

The HIMALAYA trial is the first chemotherapeutic trial to demonstrate the efficacy of combined immune checkpoint inhibitors (ICIs) for unresectable hepatocellular carcinoma (u-HCC). The STRIDE regimen used in this trial consists of a cytotoxic T-lymphocyte antigen-4 (CTLA-4) inhibitor and programmed cell death ligand 1 (PD-L1) inhibitor. Herein, we report two cases of ICI-colitis that occurred immediately after the initiation of the STRIDE regimen for u-HCC. A 73-year-old man and 75-year-old man with u-HCC were treated with the STRIDE regimen. Both patients developed grade 3 diarrhea (Common Terminology Criteria for Adverse Events, ver. 5.0) within 10 days of treatment initiation. Colonoscopy revealed aphthous erosions and erythema extending from the terminal ileum to the rectum in one case, while the other showed aphthous ulcers in the terminal ileum and shallow ulcers in the colorectum. Histopathological examination of a biopsy specimen revealed epithelial cell apoptosis and neutrophil infiltration bodies, consistent with ICI-colitis. Prednisolone (0.5 mg/kg) was effective in both patients. Our experience suggests the need for both careful monitoring and early endoscopic examination of ICI colitis in patients with unresectable HCC treated with the STRIDE regimen.