Recent Abdominal Surgery as a Risk Factor for Unfavorable Immune-Mediated Colitis Outcomes.

Background and Aims: Risk factors for immune checkpoint inhibitor (ICI) therapy enterocolitis (IMC) have not been greatly explored. Abdominal surgery can reduce bacterial diversity, increase the presence of pathogenic bacteria, and lead to inflammatory changes. This retrospective analysis seeks to determine if a history of recent abdominal surgery in patients who receive ICI therapy affects the severity and duration of enterocolitis. Methods: We retrospectively reviewed patients with history of abdominal surgeries, who received ICI for cancers and then developed IMC. Clinical profiles, oncology variables, and colitis-related characteristics were reported. Results: Seven hundred sixty-five patients met the inclusion criteria. Patients median age was 64 years, were predominantly Caucasian (78.2%), and male (58.1%). Melanoma and genitourinary cancers both had 29.5% (N = 222) patients. Programmed death-1/ligand-1 agents (50.2%) or combination therapy (44.2%) were the most common treatments. Patients with a history of abdominal surgery (N = 352) had higher rates of upper GI immune-related adverse events (24 vs 16%, Conclusion: Surgery within 3 years of IMC diagnosis confers an increased IMC severity with high rates of hospitalization, recurrence, upper gastrointestinal adverse events, and decreased overall survival. Concomitant antibiotic usage serves as an effect modifier increasing the severity of the disease course.