Positron Emission Tomography as an Imaging Biomarker in a Prospective, Longitudinal Cohort of Patients with Large Vessel Vasculitis

Abstract

Objectives

To assess the clinical value of ¹⁸F-flurodeoxyglucose (FDG) positron emission tomography (PET) in a prospective cohort of patients with large-vessel vasculitis (LVV) and disease comparators.

Methods

Patients with Takayasu’s arteritis (TAK) and giant cell arteritis (GCA) were studied, along with a comparator group consisting of patients with hyperlipidemia, diseases that mimic LVV, and healthy controls. Participants underwent clinical evaluation and FDG-PET imaging, and patients with LVV underwent serial imaging at six-month intervals. Performance characteristics of FDG-PET interpretation to differentiate clinically active LVV from disease comparators and from clinical remission were calculated. A qualitative summary score (PETVAS) based on global arterial FDG uptake was used to study associations between PET activity and clinical characteristics and to predict future relapse.

Results

170 FDG-PET scans were performed in 115 participants (LVV=56; comparators=59). FDG-PET differentiated patients with clinically active LVV and disease comparators with a sensitivity=85% (95%CI: 69–94%) and specificity=83% (95%CI: 71–91%). FDG-PET scans were interpreted as active vasculitis in most patients with LVV in clinical remission (41 of 71, 58%). Clinical disease activity status, disease duration, body mass index, and glucocorticoid use were independently associated with PET scan activity. Among patients who underwent PET during clinical remission, future clinical relapse was more common in patients with a high versus low PETVAS (45% versus 11%, p=0.03) over a median follow-up of 15 months.

Conclusions

FDG-PET provides information about vascular inflammation that is complimentary to, and unique from, clinical assessment in LVV. FDG-PET scan activity during clinical remission was associated with future clinical relapse.