18F-FDG uptake by prosthetic arterial grafts in large vessel vasculitis is not specific for active disease: results from a cohort study

Abstract

Objectives: To investigate the incidence and clinical significance of arterial graft-associated uptake of fluorodeoxyglucose in large vessel vasculitis (LVV). Background: The role of [18F]-fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT) in the management of LVV remains to be defined. Although 18FFDG uptake at arterial graft sites raises concerns regarding active arteritis or infection, its clinical significance in LVV has never been formally studied. Methods: An observational prospective study sought to identify patients with Takayasu arteritis (TA) undergoing 18F-FDG-PET/CT more than 6 months after graft surgery, from a large cohort of patients from two tertiary referral centres. 18F-FDG uptake by the graft and native arteries was scored on a 0 to 3 scale against hepatic uptake, and peri-prosthetic maximum standardized uptake value (SUVmax) was calculated. Peri-prosthetic 18F-FDG uptake in active or inactive disease was compared and arterial progression was assessed by prospective magnetic resonance angiography (MRA). Results: Twenty-six subjects with TA were enrolled. All were afebrile with negative blood culture. Peri-prosthetic uptake was significant in 23/26 patients, with a mean SUVmax of 4.21±1.46. Median peri-prosthetic 18F-FDG uptake score (3, IQR 3-3) was higher than in the native aorta (1, IQR 0-1, p<0.001). Graft-specific 18F-FDG uptake was unrelated to disease activity. Despite the high frequency of graft-associated 18F-FDG uptake, sequential MRAs did not reveal arterial progression in 25/26 patients; the remaining case showed minor progression limited to native arteries. Nine patients repeated PET/CT scanning without changes in graft-specific uptake despite increased treatment. Conclusion: Significant 18F-FDG uptake confined to arterial graft sites in patients with LVV does not reflect clinically relevant disease activity or progression. To minimise exposure to immunosuppression and in the face of negative blood culture, clinically quiescent arteritis, normal or stably raised CRP levels, we elect not to escalate treatment and monitor progression with MRA.