Association of Chronic Immune-Mediated Diarrhea and Colitis with Favorable Cancer Response.

Background: Immune-mediated diarrhea and colitis (IMDC) is a common immune-related adverse effect related to immune checkpoint inhibitors. We aimed to identify risk factors for chronic IMDC and its prognostic value in cancer outcomes. Methods: We retrospectively collected data on patients with a diagnosis of IMDC between January 2018 and October 2019 and grouped them based on disease duration into acute (<= 3 months) and chronic (>3 months) categories. A logistic regression model and the Kaplan-Meier method with log-rank tests were used for biostatistical analysis. Results: In our sample of 88 patients, 43 were in the chronic group and 45 were in the acute group. Genitourinary cancer and melanoma accounted for 70% of malignancies. PD-1/L1 monotherapy (52%) was the more frequently used regimen. We showed that chronic IMDC was associated with proton pump inhibitor use (odds ratio [OR], 3.96; P=.026), long duration of IMDC symptoms (OR, 1.05; P,.001) and hospitalization (OR, 1.07; P=.043), a histologic feature of chronic active colitis (OR, 4.8; P=.025) or microscopic colitis (OR, 5.0; P=.045), and delayed introduction of selective immunosuppressive therapy (infliximab/vedolizumab; OR, 1.06; P=.047). Chronic IMDC also reflected a better cancer response to immune checkpoint inhibitors (30% vs 51%; P=.002) and was accompanied by improved overall survival (P=.035). Similarly, higher doses of selective immunosuppressive therapy were associated with better overall survival (P=.018). Conclusions: Chronic IMDC can develop among patients with a more aggressive disease course and chronic features on colon histology. It likely reflects a prolonged immune checkpoint inhibitor effect and is associated with better cancer outcome and overall survival.