Underrecognized immune events in the emergency department among cancer patients on immune checkpoint inhibitors

Cancer patients receiving immune checkpoint inhibitor (ICI) therapy frequently present to emergency departments (EDs) with immune-related adverse events (irAEs), yet ED-based recognition remains challenging. This study aimed to describe the frequency, causes, and characteristics of ED visits among cancer patients receiving ICI therapy, and to estimate the incidence, outline severity, and explore factors possibly associated with oncologist-adjudicated irAEs.

We conducted a single-center, retrospective chart review at a university hospital ED between January 2018 and August 2024. Adult cancer patients who received ICIs (avelumab, atezolizumab, pembrolizumab, ipilimumab, or nivolumab) and presented to the ED within 90 days of their most recent treatment were included. Data collected encompassed demographics, clinical presentations, ED evaluations, management, and outcomes. A blinded oncologist independently reviewed cases to identify irAEs using the Common Terminology Criteria for Adverse Events (CTCAE v5.0).

Of 287 screened patients, 124 (43.2 %) visited the ED within 90 days post-ICI treatment, accounting for 291 ED visits. The most common presentations were fatigue, cough, and dyspnea. ED physicians explicitly diagnosed irAEs in only 3 out of 291 visits (1 %), while oncologist review identified irAEs in 40 cases (13.7 %). The predominant oncologist-adjudicated irAEs were myositis/myalgia (37.5 %) and pneumonitis (30 %). Most irAEs were low grade, with 90 % classified as CTCAE Grade 1 and 10 % as Grade 2; no Grade ≥ 3 events occurred.

Only 1 % of encounters carried an explicit irAE discharge diagnosis, with most visits coded using symptom-based terms, indicating that irAEs are infrequently documented at discharge. Although nearly all missed irAEs were low grade, greater awareness and standardized multidisciplinary protocols may improve the identification, management, and outcomes of patients presenting with ICI-related toxicities.