Validation of the immune-mediated colitis endoscopic score using a retrospective cohort of patients with immune-mediated colitis

<h2>Abstract</h2><h3>Background and Aims</h3> Immune-mediated colitis (IMC) is a challenging adverse effect of immune checkpoint inhibitor therapy, often leading to treatment interruption or discontinuation. Current IMC endoscopic scoring systems were adapted from those used for inflammatory bowel disease but fail to fully capture IMC. The newly proposed IMC endoscopic score (IMCES) seeks to help guide prognosis and treatment. We aimed to validate IMCES and explore its association with IMC clinical severity and outcomes. <h3>Methods</h3> This single-center retrospective study included patients with IMC who received immune checkpoint inhibitors and underwent endoscopic evaluation. IMCESs were calculated on the basis of 10 gross endoscopic features, as previously reported. Patients were divided into those with IMCES <4 and IMCES ≥4. Primary end points were selective immunosuppressive therapy (SIT) use, hospitalization, and clinical and endoscopic remission. <h3>Results</h3> We evaluated 807 patients, including the 308 previously used to develop IMCES, with 499 in a validation cohort. We found that IMCES ≥4 was associated with need for steroids and SIT (<i>P</i> < .05). Patients with IMCES ≥4 also tended to be hospitalized more often and longer (<i>P</i> < .05). Including ulceration as a criterion in IMCES strengthened these associations. Clinical symptoms had lower specificities for being associated with SIT use (26.8% for diarrhea, 64.6% for colitis) compared to IMCES ≥4 (91.5%). <h3>Conclusions</h3> IMCES ≥4 had a high specificity for the need for SIT and was associated with worse outcomes. Given the importance of risk stratification in the treatment of IMC to inform the early introduction of SIT, IMCES may be a powerful clinical tool to estimate prognosis and guide management but requires further validation.