Background/Purpose: The improving therapeutic approach towards childhood-onset Takayasu’s arteritis (c-TA) has decreased the mortality rate over the years and increased concerns on how to improve disease monitoring on an ongoing basis. Our aim was to assess whether 18F-FDG-PET/MRI can contribute in detecting vessel wall inflammation by increased 18F-FDG uptake in patients under immunosuppressive therapy and in apparent remission of the disease.

Methods: It was a three-center cross-sectional study where we analysed a combined imaging of 18F-FDG-PET and MRA in an integrated system. 18F-FDG-PET/MRI scan was performed in c-TA patients, alongside clinical evaluation through clinical activity score (Indian Takayasu Arteritis Clinical Activity Score – ITAS2010 and Pediatric Vasculitis Activity Score – PVAS), and damage score (Takayasu Arteritis Damage Score – TADS and Pediatric Vasculitis Damage Index – PVDI) and laboratorial analysis providing measures of ESR, CRP, HMGB1 (High Mobility Group Box 1), IFN-γ, IL-10, IL-12p70, IL -1ra, IL-1β, IL-6, TNF-α, VEGF and PDGF. There were control groups for the serum and plasma cytokine levels (healthy controls) and for arterial 18F-FDG-PET/MRI (oncologic patients) findings.

Results: Seventeen c-TA patients (65% females) between the ages of 6 and 21 years, with median disease duration of 9.4 years were recruited. Only 1 patient presented clinical disease activity according to the ITAS2010 and 6 of them (35.6%) had increased ESR and/or CRP. The most frequent MRA finding was stenosis, followed by thickness, visualized in 82.4% and 75%, respectively. 18F-FDG-PET revealed that 88.2% patients had FDG uptake higher than liver (visual score=3) in at least 1 arterial segment. The qualitative assessment of vascular FDG uptake across the arterial segments – PETVAS – was 21.8 ± 3.3. Median SUVmax was 3.22 (2.76-3.69) and mean metabolic inflammatory volume (MIV) was 1990cm3 ± 1077. Patients presented significantly higher SUVmax than controls (p< 0.001). Plasma IFN-γ levels showed a tendency to be higher in patients compared to controls (p=0.052). There was a negative moderate correlation between aortic wall thickness extent and IL-1ra (Rho= -0.662; p= 0.037). Finally, there was a positive moderate correlation between SUVmax and CRP levels (Rho=0.528; p= 0.029) and also with MIV value (Rho=0.615; p=0.009).

Conclusion: This study applied a state-of-the-art imaging modality that revealed a strong vascular FDG uptake regardless of the clinical and laboratorial assessments. We suppose that this finding may mean a silent activity in the vessel wall. However, only a prospective international multicentre initiative could clarify whether these changes will lead to further arterial lesion progression and would help to guide the therapy more adequately for c-TA.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/is-positron-emission-tomography-magnetic-resonance-imaging-pet-mri-a-reliable-tool-for-detecting-vascular-activity-in-treated-childhood-onset-takayasus-arteritis-c-ta-a-multicenter-study/