Risk of Colitis in Patients With Inflammatory Bowel Disease or Microscopic Colitis Exposed to Checkpoint Inhibitors: A National Danish Cohort Study.

[PURPOSE] Patients with intestinal inflammatory diseases such as ulcerative colitis (UC), Crohn's disease (CD), and microscopic colitis (MC) are excluded from clinical trials with immune checkpoint inhibitors (ICI) because of concerns of exacerbating their underlying immune-mediated disease. This study evaluated the risk of developing disease activity or checkpoint inhibitor checkpoint inhibitor-mediated enterocolitis (IMC).

[MATERIALS AND METHODS] We performed a nationwide, retrospective cohort study in Denmark, analyzing patients with UC, CD, and MC diagnosed with cancer and treated with ICIs between 2010 and 2024.

[RESULTS] Eighty-five patients were included, and IMC was observed in 39 (46%) patients. Of these, 15 cases were mild, allowing 61 (72%) patients to continue ICI treatment. Multivariate logistic analysis showed that patients with CD had a lower odds ratio (OR) for developing IMC compared with patients with UC and MC (OR, 0.07, = .02). When compared with a control cohort without intestinal disease (n = 81), patients with UC, CD, and MC had a significantly higher risk of developing IMC when treated with anti-PD-1/anti-PD-L1 inhibitors, with a hazard ratio of 4.93, < .001.

[CONCLUSION] Patients with CD appear to have a lower risk of IMC than those with UC and MC. Despite an increased risk of IMC and severe IMC in patients with UC, CD, and MC, 72% of the patients were able to continue first-line treatment with ICI. Treatment with ICI in patients with UC, CD, and MC is overall well tolerated and should be considered on the basis of the same criteria as in patients without intestinal diseases.