Emergency Department Utilization Among Cancer Patients Receiving Immune Checkpoint Inhibitors: Patterns, Clinical Characteristics, and Associated Factors

Abstract

Background: Immune checkpoint inhibitors (ICIs) have become an integral component of cancer treatment across multiple solid and hematologic malignancies. Although these agents can produce durable clinical responses, they are also associated with immune-related adverse events that may lead to emergency department (ED) visits. However, real-world data describing ED utilization among patients receiving ICIs in Saudi Arabia remain limited. Objectives: This study aimed to describe all-cause ED utilization among patients with cancer receiving immune checkpoint inhibitors, characterize immune-related and non-immune-related ED presentations, and explore factors associated with ED use. Methods: This retrospective observational cohort study included adult patients with cancer who received at least one immune checkpoint inhibitor at King Abdullah Medical City, Makkah, Saudi Arabia, between January 2019 and December 2023. Patients were followed for a predefined 24-week period after the first documented administration of an ICI. The primary outcome was the occurrence of at least one all-cause ED visit. Secondary outcomes included ED visits attributed to irAEs, documented toxicity patterns, management, hospitalization, and exploratory factors associated with ED utilization. Logistic regression analyses were exploratory and not intended to establish causal associations. Results: A total of 288 patients were included. The mean age was 58.4 ± 13.69 years, and most patients were male. The most common cancer types were non-small cell lung cancer, renal cell carcinoma, and urothelial carcinoma. Pembrolizumab was the most frequently used immune checkpoint inhibitor. During the 24-week observation period, 162 patients (56.3%) had at least one ED visit, whereas 25 patients (8.7% of the total cohort) had an ED visit attributed to an irAE. Gastrointestinal, dermatologic, and endocrine toxicities were the most frequently documented irAE categories. Most toxicities were graded as grade 1 or 2. In exploratory regression analyses of all-cause ED utilization, treatment-cycle count, alanine aminotransferase, and total bilirubin were statistically associated with ED visits. These associations should be interpreted cautiously because treatment-cycle count was not a fixed baseline exposure, laboratory timing could not be fully standardized retrospectively, and residual confounding may remain. Conclusions: ED utilization was common among patients receiving ICIs, whereas only a minority of patients had ED visits attributed to irAEs. These findings primarily characterize real-world acute healthcare utilization in a Saudi tertiary oncology setting. Associations identified in exploratory analyses should not be interpreted as causal or as specific predictors of immune-mediated toxicity. Further prospective studies are needed to evaluate structured approaches for assessing acute presentations in patients receiving ICIs.