As immune checkpoint inhibitors become a cornerstone of modern oncology, the rheumatic complications they trigger are emerging as a serious and underappreciated management challenge. Understanding their frequency, severity, and treatment resistance matters not just for oncologists but for any clinician involved in the care of cancer survivors navigating long-term health consequences.
The German ERIN Registry, a multicenter observational cohort, enrolled 60 adults receiving immune checkpoint inhibitors (ICIs) who were referred to rheumatologists for immune-related adverse events (irAEs). The dominant clinical presentation was a rheumatoid arthritis-like polyarthritis, accounting for roughly 42% of cases, followed by polymyalgia rheumatica-like and peripheral spondyloarthritis-like syndromes. Strikingly, 90% of patients experienced moderate or severe disease, nearly a quarter required hospitalization, and 38% ultimately had their cancer immunotherapy permanently discontinued due to these complications. While systemic glucocorticoids were deployed in 85% of patients, more than half proved glucocorticoid-refractory, necessitating second-line immunosuppressive therapy. Younger patients were disproportionately represented among those developing axial spondyloarthritis-like presentations.
This registry captures a clinical reality that randomized ICI trials have historically underrepresented: rheumatic irAEs are not mild, self-limiting nuisances but complex inflammatory syndromes that can rival primary rheumatic disease in severity. The finding that over half of treated patients are steroid-refractory is particularly significant, as it signals that standard oncology-level irAE management protocols — which often default to short glucocorticoid courses — are insufficient for this subset. The 38% permanent ICI discontinuation rate also raises a difficult therapeutic tradeoff, as stopping immunotherapy may compromise tumor control. Limitations include the relatively small cohort size (n=60), the referral bias inherent to a rheumatologist-based registry (likely skewing toward more severe cases), and the observational design precluding causal inference. Nonetheless, this registry advances the case for systematic, subspecialty-integrated irAE monitoring in all ICI-treated patients, particularly as checkpoint inhibitor use expands across cancer types.