Immune-Related Adverse Events: Findings From a Population-Based Study

Immune checkpoint inhibitors (ICIs) are effective for several tumor entities but cause immune-related adverse events (irAEs). These side effects may affect any organ and often lead to ICI discontinuation, hospitalization, long-term complications, or sequelae. To assess the burden of irAEs, this longitudinal observational study analyzed their incidence and the frequency of related hospitalizations using anonymized health claims data from a payer database covering 5.8 million insured individuals in Germany. Patients with hepatocellular carcinoma (HCC), non-small cell lung cancer (NSCLC), renal cancer, urothelial cancer, or skin cancer who started ICI therapy between 2017 and 2020 were selected using ICD-10 GM (International Statistical Classification of Diseases, German Modification) codes. The incidence of irAEs and related hospitalizations within 6 months was assessed using predefined ICD-10 codes in both inpatient and outpatient settings. A total of 6350 patients (mean age: 66.8 y) with NSCLC (n=4797), skin cancer (n=1266), HCC (n=1249), renal (n=1183), or urothelial cancer (n=656) initiated ICI therapy between 2017 and 2020. The incidence of any new-onset irAE was 31.4% (95% CI: 30.3%-32.6%). New-onset respiratory irAEs were the most common [11.7% (95% CI: 11.0%-12.5%)], followed by gastrointestinal irAEs (7.8%; 95% CI: 7.1%-8.5%). Skin cancer patients most frequently developed gastrointestinal irAEs, while other tumor types showed more respiratory irAEs. Using an inclusive definition that also captures exacerbations of pre-existing conditions, nearly half of patients experienced at least one hospitalization with an irAE recorded as the main discharge diagnosis within 6 months after ICI initiation. These findings underscore the importance of monitoring and management to reduce patient and healthcare impact.