A scoping review of vasculitis as an immune-related adverse event from checkpoint inhibitor therapy of cancer: Unraveling the complexities at the intersection of immunology and vascular pathology.

BACKGROUND/PURPOSE: Vasculitis as an immune-related adverse event (irAE) from checkpoint inhibitor therapy (ICI) to treat cancer is a rare clinical event, and little is known regarding its nosology, clinical manifestations, or response to treatment and outcomes.

METHODS: To address these gaps, we used the Preferred Reporting Items for Systemic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) framework to further define this complication. Two independent PUBMED searches in September and November of 2022 revealed 127 publications with 37 excluded from title by relevance, 43 excluded by article type, and 23 excluded due to lack of biopsy results, or biopsy negative for vasculitis. Twenty-nine documented cases from 24 publications were included for final analysis. Basic demographics, ICI details, timing of onset of vasculitis symptoms, irAE treatment and outcomes were collected. The vasculitides were classified using 2022 ACR/EULAR Vasculitis Classification Criteria as well as 2012 Revised Chapel-Hill Nomenclature. Adaptations from Naidoo et al. 2023 [1] consensus definitions for irAEs were used and efforts were made to classify steroid-responsive versus unresponsive irAEs.

RESULTS: Of the 29 cases reviewed, the average age of patients was 62.1 ± 11.0, composed of 58.6 % (n = 17) male and 41.3 % (n = 12) female. Prominent cancer types were lung cancer (41.4 %; n = 12), melanoma (41.4 %; n = 12), and renal cancer (10.3 %; n = 3), with majority being stage 4 (75.9 %, n = 22) and stage 3 (10.3 %, n = 3). Only 8 cases met the ACR/EULAR criteria, and by Chapel-Hill Nomenclature, approximately a third were small-vessel vasculitis (31.0 %; n = 9) with n = 4 positive for ANCA. Most biopsies were taken from the skin (37.9 %, n = 11) and kidney (24.1 %, n = 7). Patients were either treated with single (65.5 %, n = 19), dual (17.2 %; n = 5), or sequential (17.2 %; n = 5) ICI regimen which included anti-PD-1 therapy in all but one case, with mean of 8.7 ± 10.5 cycles received. Mean time to onset of symptoms from start of ICI was 7.2 ± 7.8 months, with 55.2 % occurring >3 months since the initial immunotherapy. Vasculitis treatment included glucocorticoids in 96 % of cases and immunotherapy was often discontinued (44.8 %; n = 13). Clinical improvement of irAE was documented in 86.2 % (n = 25). Data were missing in terms of fate of ICI (34.5 %; n = 10) and tumor outcomes (41.4 %; n = 12). Cancer progressed in 20.7 % (n = 6), stable in 34.5 % (n = 10) cases, and 6 patients died of all-causes.

CONCLUSION: Vasculitis as an irAE appears clinically heterogeneous and rare. Among reported cases with adequate documentation, vasculitis is of delayed onset following the initiation of immunotherapy. Outcomes of ICI-vasculitis were generally favorable, responding to glucocorticoids and immunotherapy withdrawal. There is an urgent need for more standardized reporting of rare irAEs such as vasculitis to clarify clinical risks, classification, relationship to immunotherapy and outcomes.