Imaging to predict early relapses after treatment discontinuation in patients with large vessel giant cell arteritis – A cohort study

Objectives To investigate the value of [18F]fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) and magnetic resonance imaging (MRI) in predicting relapse after treatment discontinuation in patients with large-vessel giant cell arteritis (LV-GCA). Methods This study included patients with LV-GCA whose treatment was discontinued between 2018 and 2023. All patients underwent PET/CT and/or MRI at the time of treatment discontinuation in clinical remission. Qualitative and quantitative PET/CT scores, by measuring standardized uptake values (SUV), and semiquantitative MRI scores of the aorta and supraaortic vessels were compared between patients who relapsed within 4 months after treatment discontinuation and those who did not. Results Forty patients were included (median age 67.4 years, interquartile range (IQR) 60.8–74.0; 77.5 % females). Eleven patients (27.5 %) relapsed after treatment discontinuation (time to relapse 1.9 months, IQR 1.4–3.3). Patients who relapsed were comparable to those who remained in remission with respect to the presence of active vasculitis on MRI and/or PET/CT (54.5% vs. 58.6 %, p = 1.0), the number of segments with vasculitic findings on MRI (0, IQR 0.0–1.5, vs. 2, IQR 0.0–3.0, p = 0.221) or the highest SUV artery/liver ratio on PET/CT (1.5, IQR 1.4–1.6, vs. 1.3, IQR 1.2–1.6, p = 0.505). The median number of vasculitic segments on PET/CT was 2.5 (IQR 0.5–4.5) in those with vs. 0 (IQR 0.0–1.5, p = 0.085) in those without relapse, and the PET/CT scores 4.5 (IQR 0.75–8.25) vs. 0 (IQR 0.0–3.0, p = 0.172). Conclusion PET/CT or MRI at treatment stop did not predict relapse and may not be suited to guide treatment decisions in patients with LV-GCA in remission.