Limb arteries involvement assessed by FDG/PET CT at diagnosis of giant cell arteritis and risk of relapse: an observational study

Introduction Steroids and anti-IL6 biotherapy are highly effective in obtaining remission in patients with giant cell arteritis (GCA) but the risk of relapses remains high. We aimed to identify predictors of relapse in GCA.Methods All consecutive patients admitted with a new diagnosis of GCA - according to the 2022 American College of Rheumatology/EULAR (ACR/EULAR) classification criteria - between May 2011 and May 2022 were eligible for this study. The primary outcome was the GCA relapse rate over the 36-months follow up. Factors associated with the primary outcome and time to first relapse were analyzed.Results One hundred and eight patients (74 [69-81] years, 64.8% women) with a new diagnosis of GCA were studied. GCA was biopsy-proven in 65 (60.2%) cases. Ninety-eight (90.7%) FDG/PET CT scans performed at diagnosis were available for review. All patients received steroids given for 21.0 [18.0-28.5] months, associated with methotrexate (n=1, 0.9%) or tocilizumab (n=2, 1.9%). During a median follow-up of 27.5 [11.4-35.0] months, relapse occurred in 40 (37%) patients. Multivariable Cox regression model, including general signs, gender, aortic wall thickness, FDG uptake in arterial wall and IV steroid pulse as covariates, showed that both general signs (HR 2.0 [1.0-4.0, p<0.05) and FDG uptake in limb arteries (HR 2.7 [1.3-5.5], p<0.01) at diagnosis were associated with GCA relapse.Conclusion FDG uptake in limb arteries at diagnosis is a predictor of relapse in newly diagnosed GCA