Challenge of immune-mediated adverse reactions in the emergency department.

Multiple drugs of a new class of cancer treatments called immune checkpoint inhibitors, which work by enabling the immune system to attack tumour cells, have been approved for a variety of indications in recent years. Immune checkpoints, such as cytotoxic T-lymphocyte antigen-4 and programmed death-1, are part of the normal immune system and regulate immune activation. Treatment with inhibitors of these checkpoints can significantly improve response rates, progression-free survival and overall survival of patients with cancer; it can also result in adverse reactions that present similarly to other conditions. These immune-mediated adverse reactions (IMARs) are most commonly gastrointestinal, respiratory, endocrine or dermatologic. Although patients' presentations may appear similar to other types of cancer therapy, the underlying causes, and consequently their management, may differ. Prompt recognition is critical because, with appropriate management, most IMARs resolve and patients can continue receiving immune checkpoint inhibitor treatment. Rarely, these IMARs may be life-threatening and escape detection from the usual evaluations in the emergency environment. Given the unusual spectrum and mechanism of IMARs arising from immune checkpoint inhibitors, emergency departmentED staff require a clear understanding of the evaluation of IMARs to enable them to appropriately assess and treat these patients. Treatment of IMARs, most often with high-dose steroids, differs from chemotherapy-related adverse events and when possible should be coordinated with the treating oncologist. This review summarises the ED presentation and management of IMARs arising from immune checkpoint inhibitors and includes recommendations for tools and resources for ED healthcare professionals.