The Impact of Fecal Diversion on Immune Checkpoint Inhibitor Adverse Gastrointestinal Toxicities

Background/Objective: Immune checkpoint inhibitors (ICIs) are highly effective cancer therapies used across a broad spectrum of malignancies. They function by disrupting immune inhibitory pathways, resulting in an amplified immune response against tumors. However, this heightened immune activity can predispose patients to immune-mediated colitis (IMC), which is graded using the Common Terminology Criteria for Adverse Events (CTCAE) and can range from mild diarrhea to severe colitis. Prior studies have shown that fecal stream diversion can modify the gut microbiome and influence the severity of intestinal inflammation. This study investigates the impact of fecal stream diversion on IMC outcomes in cancer patients receiving ICIs. Methods: We conducted a retrospective cohort study of patients treated with ICIs from 2016 to 2023 who had a history of fecal stream diversion. Demographic, oncologic, and toxicity-related data were collected. Patients with active gastrointestinal infections, autoimmune GI diseases, or graft-versus-host disease were excluded. Descriptive statistics and univariate and multivariate logistic regression analyses were performed using SAS version 9.4. Results: A total of 44 patients were included and categorized into two groups based on the timing of bowel stoma creation relative to the IMC event. CTCAE grade for diarrhea was used to assess GI toxicity. While overall CTCAE grade distribution for diarrhea did not differ significantly between groups (p = 0.22), Hispanic ethnicity was significantly associated with a lower CTCAE grade compared to non-Hispanic or Latino individuals (OR [95% CI] = 0.12 [0.02, 0.62], p = 0.011). In contrast, higher CTCAE grades were significantly associated with ileostomy versus colostomy (OR [95% CI] = 3.21 [1.01, 10.18], p = 0.048) and in patients without an ostomy at the time of diarrhea onset compared to those with an ostomy (OR [95% CI] = 8.87 [2.51, 31.31], p = 0.0007). Conclusions: Our findings suggest that the CTCAE diarrhea grade is significantly associated with ethnicity, type of stoma, and presence of ostomy at the time of diarrhea. Limitations include the retrospective study design and small sample size. These results contribute to understanding potential strategies for mitigating the serious gastrointestinal toxicities of ICIs.