Giant cell arteritis (GCA) is the most common vasculitis in subjects over 50 years of age in Western countries [1]. Its particular tropism for the external carotid artery and its dividing branches may be clinically manifested by headaches, scalp tenderness, jaw claudication and vision loss.

Improvement of vascular imaging in recent decades has greatly increased the detection of this involvement, currently estimated to affect 45-65% of patients at diagnosis depending on the imaging techniques used in prospective studies [2], [3], [4]. Thus, it is possible to individualize different phenotypes of GCA; the cephalic form and the large vessels vasculitis (LVV) with aortic and/or large peripheral vessel involvement as well as a combination of different phenotypes.

Considering the risk of complications associated with aortitis (aneurysm, dissection), aorta imaging is now recommended at GCA diagnosis [5], [6], [7], [8]. Computed tomography angiography (CTA), 18Fluorine-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT), and magnetic resonance angiography (MRA) are the main aortic imaging modalities. CTA provides high-resolution analysis of the aortic wall, with a regular circumferential thickening ≥2.2mm being highly suggestive of aortitis in the absence of atherosclerosis [9]. PET/CT offers a mapping of all involved arteries, including aorta main branches for which inflammation may be difficult to assess with CTA [10]. Circumferential vascular FDG uptake over liver background is considered specific for aortitis [11]. The diagnostic performances of CTA and PET/CT in GCA appears to be similar [10,12].

Data regarding the prognosis of aortitis remain heterogeneous because imaging is performed at different times over the course of the disease and the methods of image acquisition are not yet sufficiently standardized. Several studies have suggested a deleterious role of LVV compared to isolated cephalic forms, associated with an increased risk of relapse and aortic complications [6,13,14]. Among patients with LVV, the ability of global arterial FDG uptake (PETVAS) to predict future clinical relapse is controversial [15,16]. To date, no study has focused on the prognostic value of GCA-associated aortitis according to the initial imaging method.

This study aimed to compare the risk of relapse of patients with GCA-associated aortitis according to the presence of aortitis on CTA and/or on PET/CT.