Introduction With the rising use of immune checkpoint inhibitors (ICIs) in oncology, emergency physicians are increasingly confronted with their immune-related adverse events (irAEs). We described the types of irAEs presenting to the ED of a Belgian cancer centre and determined associations with the development of an irAE and other patient’s characteristics. Secondary objectives describe the therapeutic management and determine 7 and 30-day mortality.

Methods A retrospective chart review of ED visits of patients on ICI from 15 December 2016 to 6 December 2020 was performed. Clinical presentation, cancer characteristics and type of ICI were extracted by a single abstractor. We recorded any suspicion of irAE in the ED and confirmation of an irAE was based on the patient’s oncologist report. Outcome was based on mortality at date of last follow-up.

Results 227 patients on ICI presented to the ED, with a total of 451 visits. 54 (12%) of the visits resulted in a diagnosis of irAE. Four clinical features were associated with an irAE: gastrointestinal complaints (p=0.01), skin rashes (p=0.02), acute renal failure (p=0.002) and abnormal liver function (p=0.04). An irAE was also associated with three different factors: a cancer status in remission (OR=5.33, 95% CI 2.57 to 11.04), a combination of two ICIs (OR=4.43, 95% CI 2.09 to 9.42) and a medical history of irAE (OR=2.44, 95% CI 1.27 to 4.68). 30-day mortality was lower in the irAE group (0%) than in the non-irAE group (13%, 95% CI 9% to 19%).

Conclusions Oncological patients under ICI presenting in the ED are more likely to have an irAE if they present with gastrointestinal and dermatological complaints, acute renal failure and abnormal liver function. This is also true for patients with any history of irAE, a concomitant use of two ICIs and with a cancer status in remission.