Immune checkpoint inhibitor-related gastrointestinal toxicity in patients with malignancy involving the luminal gastrointestinal tract and its impact on cancer outcomes.

Background: Immune checkpoint inhibitors (ICI) are known to cause immune-related adverse events (irAE) with the gastrointestinal (GI) tract among the most affected. Our knowledge of GI irAE in patients with luminal GI malignancies is poor. We aimed to characterize the incidence, clinical features, treatment, and outcomes of these GI irAEs. Methods: This was a retrospective study of patients with malignancies involving the luminal GI tract and GI irAEs at MD Anderson Cancer Center from January 2010 to June 2020. Clinical data were collected and analyzed. Results: Eighteen patients with luminal GI tract malignancies treated with ICIs had evidence of GI irAEs based on clinical symptoms and/or histology. The predominant GI irAE symptom was diarrhea (78%). Ten had non-ulcerative inflammation (56%) and 5 had ulcerative inflammation (28%) on endoscopy. Histologically, 3 patients (17%) had evidence of acute inflammation, 4 (22%) had chronic inflammation, and 9 (50%) had both. Ten patients (56%) received immunosuppressant treatment, which included steroids alone (n=2, 20%), steroids with biologics (infliximab or vedolizumab) (n=7, 70%), or biologics alone (n=1, 10%), with clinical remission in all cases. Of the 6 patients who previously had stable or ICI-responsive cancer and received immunosuppressants, none developed progression of GI luminal malignancy during the study period. Conclusions: GI irAEs occurred in 2.4% of patients treated with ICI for cancer involving the luminal GI tract. Immunosuppressant therapies (e.g., vedolizumab) appear to be effective for GI irAEs, showing no association with further GI luminal cancer progression, recurrence, or a subsequent poor response to ICI therapy.