Immune Checkpoint Inhibitor Associated Large Vessel Vasculitis: A Case Series from the Canadian Research Group of Rheumatology in Immuno-Oncology

Objectives The use of immune checkpoint inhibitors (ICI) for cancer treatment continues to increase as indications expand, both in the palliative and adjuvant setting. Immune related adverse events (irAE) can affect any organ due to immune system stimulation. ICI associated large vessel vasculitis (ICI-LVV) is a rare irAE, with descriptions limited to small case series and reports.[1] We aimed to identify and characterize the manifestations, management and outcomes of ICI-LVV in a national multi-center cohort. Methods We searched the Canadian Research Group of Rheumatology in Immuno-Oncology (CanRIO) retrospective and prospective cohorts for cases of de novo ICI-LVV. Cases of pre-existing LVV were excluded. Demographic, clinical and laboratory data were extracted from the study databases. Results We identified 13 patients who developed LVV after ICI exposure, most commonly for melanoma (n=5) and non-small cell lung cancer (n=3). Most patients received single agent ICI (69%). The median time from ICI exposure to symptom onset was 4.0 months (IQR 1.5-15). Isolated large vessel (n=5) or isolated cranial involvement (n=5) were the most common presentations. In those with cranial involvement (n=8), headache (n=8), jaw claudication (n=6) and scalp tenderness (n=6) were the most common symptoms. In those with confirmed large vessel involvement, (n=8), the most common radiographic finding was hypermetabolism on PET scan (n=6), often found incidentally without associated symptoms. There was 1 case of stenosis, and no aneurysms identified on imaging. Six patients had temporal artery biopsy and 2 were consistent with LVV, without clear histopathologic differences from idiopathic giant cell arteritis. Eleven patients were treated with glucocorticoids: Two relapsed during taper, 1 required additional immunosuppression (methotrexate and tocilizumab). Two patients with normal inflammatory markers and isolated large vessel involvement (hypermetabolism on PET) had remission without treatment. Only 2 patients continued ICI after ICI-LVV diagnosis, both without vasculitis recurrence/progression. There was no vision loss or death attributable to ICI-LVV. Conclusion Isolated cranial or large vessel involvement were the most common presentations of ICI-LVV. Like idiopathic GCA, headache was the most common clinical manifestation in those with cranial involvement. In contrast, isolated large vessel involvement was commonly found on PET, incidentally and without clinical symptoms. Careful clinical correlation is required in cases of isolated large vessel involvement, as not all may require treatment. This has important implications given the potential impact of immunosuppression on ICI and tumor outcomes. Further studies are needed into the clinical presentation, underlying pathological mechanisms and optimal management of ICI-LVV. References [1.] Cottu A. Rheumatology (Oxford) 2025;64:4546-54.