Abstract 736: Treatment with immune checkpoint inhibitors (ICIs) and the occurrence of colitis among patients with melanoma in the United States
Authors: Pan Xianying , Verma Devashish , Zhang Jiayin , Pathak Raminder , Monda Stefano , Ma Xiaomei 
Published: April 2023

Abstract
Background: Immune checkpoint inhibitors (ICIs) have improved the survival of cancer patients, but their use comes with the risk of immune-related adverse events. We evaluated the association between ICI treatment and the occurrence of colitis in patients with melanoma using a propensity score matched case-control design nested within a retrospective cohort.
Methods: Using the United Healthcare (Optum Clinformatics) Closed Claims & Lab Results Database (01/01/2016 - 12/31/2021), we assembled a cohort of adult patients with melanoma who fulfilled the following eligibility criteria: 1) had ≥2 outpatient claims at least 30 days apart or ≥1 inpatient claim with an International Classification of Diseases (ICD) code indicative of melanoma; 2) received cancer treatment (surgery, chemotherapy, radiotherapy, ICI, or targeted therapy); 3) had a claim with a melanoma ICD code within 5 days before first cancer treatment (i.e., baseline); 4) had ≥12 months of continuous insurance coverage before baseline; 5) had no missing data on age, sex, race, and geographic region; and 6) had no claims for colitis in the 12 months before baseline. From the baseline cohort of 14,781 melanoma patients, cases with colitis were identified if they had ≥1 claim with a colitis ICD code during follow-up (i.e., from baseline to end of insurance coverage, or 12/31/2021), followed by claims for colitis medications within 30 days. Controls were melanoma patients without any colitis claims and were matched to cases with a 10:1 ratio using propensity scores, which were developed using a logistic regression model with colitis being the dependent variable and all available sociodemographic factors (age, sex, race, and region) and comorbidities identified from the 12 months before baseline as independent variables. For controls, we identified their ICI treatment through a specific date so that their follow-up time was the same as that of their matched case. We then conducted conditional logistic regression to estimate the association between ICI treatment and occurrence of colitis.
Results: A total of 264 colitis cases (64.8% received ICI) and 1,906 controls (10.9% received ICI) were included. Cases and controls were balanced with respect to the variables associated with colitis occurrence (all standardized differences &lt;0.1), indicating adequate matching based on propensity scores. Melanoma patients who underwent ICI treatment were more likely to develop colitis during follow-up, compared with controls (odds ratio = 19.1, 95% confidence interval: 13.4-27.2; p&lt;.001).
Conclusions: In a large cohort of patients treated for melanoma during 2016-2021, treatment with ICIs, compared with the other treatments, was associated with a 19-fold increase in the odds of colitis occurrence. Further research is needed to identify melanoma patients at risk for colitis to facilitate early treatment and improve patient outcomes.
Citation Format: Xianying Pan, Devashish Verma, Jiayin Zhang, Raminder Pathak, Stefano Monda, Xiaomei Ma. Treatment with immune checkpoint inhibitors (ICIs) and the occurrence of colitis among patients with melanoma in the United States [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 736.