PET-Derived Increased Inflammation in Large Vessels is linked to Relapse-Free Survival in Patients with Giant Cell Arteritis

Background Despite anti-inflammatory treatment, patients with giant cell arteritis (GCA) experience relapse. We aimed to determine respective relapse predictors focusing on [ (18) F]fluorodeoxyglucose ([ (18) F]FDG)-PET-based parameters. Material and Methods 21 therapy-naïve GCA patients received [ (18) F]FDG-PET/CT. Patients were divided in two groups: those who relapsed during course of disease and those who did not. Median follow up was 15 months. [ (18) F]FDG-PET/CT was analyzed for visual (PET vascular activity score [VAS]) and quantitative parameters, including Target-to-background-Ratio with liver (TBR (liver) ) and jugular vein (TBR (jv) ) serving as reference tissues. In addition, clinical parameters were tested. Results 8/21 (38.1 %) had relapse. Clinical parameters could not significantly discriminate between relapse vs no-relapse, including age (p = 0.9) or blood-based inflammatory markers (white blood cell counts [WBC] and c-reactive protein [CRP], p = 0.72, each). PETVAS score could also not differentiate between respective subgroups (p = 0.59). In a quantitative assessment, TBR (jv) demonstrated a trend towards significance (p = 0.28). TBR (liver) , however, separated between patients with and without relapse (p = 0.03). Conclusion [ (18) F]FDG PET quantification of vessels may be useful to identify GCA patients prone to relapse during follow-up.