Background/Purpose: There is limited prospective data characterizing arterial lesions over time in giant cell arteritis (GCA) and Takayasu’s arteritis (TAK), the two main forms of large-vessel vasculitis (LVV). FDG-PET can detect vascular inflammation. Whether vascular PET findings predict angiographic change is unknown.

Methods: Patients with GCA or TAK were recruited into a prospective, observational cohort. All patients underwent magnetic resonance (MR) or computed tomography (CT) angiography and a follow-up study ≥6 months after baseline per a standardized imaging protocol. Arterial lesions, defined as stenosis, occlusion, or aneurysm, were evaluated in 4 segments of the aorta and 13 branch arteries by a central reader blinded to clinical status. Development of new lesions in these same territories was recorded, and existing lesions were characterized as improved, worsened, or unchanged over time.

All patients underwent FDG-PET on the same date as angiography. Qualitative assessment of FDG uptake was performed in each corresponding arterial territory evaluated by angiography. Active vasculitis was defined as greater FDG uptake in the arterial wall compared to the liver by visual inspection.

Conditional logistic regression using a within-person matched design selecting for cases of asymmetric angiographic progression in paired arterial territories (e.g. bilateral subclavian arteries) was performed to evaluate whether FDG-PET activity was independently associated with angiographic progression, controlling for all person-level confounders.

Results: 1162 arterial territories were evaluated from 70 patients with LVV (TAK=38; GCA=32). Over 1.6 years of median follow-up, new lesions developed only in 8 arterial territories, exclusively in 5 patients with TAK. Arterial lesions improved in 16 territories (GCA = 7, TAK = 9) and worsened in 6 territories (GCA = 1, TAK = 5). Typically, angiographic change was asymmetric in paired arteries (26/30 territories).

FDG-PET activity was evaluated in 1091/1162 (94%) of corresponding arterial territories. PET activity in an arterial territory at baseline was significantly associated with change in that arterial territory on follow-up angiography (p< 0.01), with a sensitivity of 80% and specificity of 74% (FIGURE). Most arterial territories without PET activity at baseline remained unchanged over time by angiography, yielding a negative predictive value of 99%. Most territories with PET activity also did not show change over time, but of the territories with angiographic change, the majority had PET activity (24/30 territories). Using conditional logistic regression, an arterial territory with baseline PET activity had a 3-fold increased risk for angiographic progression of disease compared to the paired arterial territory without PET activity (p< 0.01).

Conclusion: Development of angiographic change was infrequent in this cohort of patients with LVV. Lack of PET activity was strongly associated with stable angiographic disease. Most cases of angiographic change were asymmetric in paired arterial territories with PET activity present only in the affected side at baseline. These data may inform recommendations for imaging monitoring in LVV.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/18f-fluorodeoxyglucose-positron-emission-tomography-as-a-predictor-of-angiographic-progression-of-disease-in-large-vessel-vasculitis/