THU0311 PERSISTENT LOW-GRADE VASCULAR INFLAMMATION IN LARGE VESSEL VASCULITIS: A LONGITUDINAL STUDY USING FULLY INTEGRATED 18F-FDG PET/MR
Authors: Roberto Padoan, Mara Felicetti, Filippo Crimì, Federica Padovano, Carmelo Lacognata, Diego Cecchin, Pietro Zucchetta, Franco Schiavon
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background:</h3> Persistent low-grade vascular inflammation in large vessel vasculitis (LVV) treated patients could represent the expression of persistent subclinical disease activity or post-inflammatory vascular remodelling. Whether these findings have any impact on future vascular outcomes is still an unmet need<sup>1</sup>. <h3>Objectives:</h3> To evaluate the frequency and evolution of the low-grade vascular inflammation using a fully integrated 18F-FDG PET/MR in a longitudinally followed cohort of LVV patients. <h3>Methods:</h3> All consecutive patients with LVV who underwent at least 2 PET/MR scans (median time 9[6] months) between January 2015 and January 2019 were included. For each scan vessel's metabolic activity was assessed using the Meller's grading and the standard uptake value<sup>2</sup>. Low-grade inflammation was defined as Meller 1 and 2 (inferior or equal to liver), as previously reported. Demographic and clinical data, as well as disease remission or flares, were recorded and compared to vascular metabolic activity. <h3>Results:</h3> In total, 107 PET scans were performed (from min. 2 scans to max. 5 scans per patient), mainly during follow-up (78.8%) in 33 LVV patients (72.7% GCA, 27.3% TAK), predominantly female (84.8%), with a regular BMI (24.1[5.3]) and with a long-standing disease (30[29] months). At PET examination, low-grade metabolic activity was reported in 60% of the cases (86.4% GCA and 13.6% TAK), while complete remission in 15% and highly pathological in 25%. Comparing patients with low-grade vascular inflammation to those with complete remission (Meller 0), they resulted significantly older (64[12] vs 57[33] years, p=0.005), with a lower disease duration (26.5[21.4] vs 52.5[34.8] months, p=0.001) and with higher daily prednisone dosage, but without significance (5[7.5] vs 2.5[8.75], p=0.096). No significant differences were noted in acute phase reactants and type of treatment. Moreover, when compared to those with high metabolic activity (Meller 3), patients with low-grade inflammation resulted significantly older (64[12] vs 62[25] years, p=0.025), with a lower disease duration (26.5[21.4] vs 33[46] months, p=0.041), lower CRP level, but without significance (3.05[5.92] vs 10.35[13.75], p=0.069). Clinical remission, before PET examination, was registered in 55.6% of patients with Meller 3 activity, significantly lower compared to those with Meller 1+2 (87.5%, p=0.002). Steroids and immunosuppressants tapering rate did not differ between patients with low-grade metabolic activity and those without activity. Among all patients with low-grade vascular inflammation, 60% underwent to steroids or immunosuppressants tapering. At the subsequent PET examination, a persistence/worsening of metabolic activity was found in 88.9% of them. Change or increase of the treatment regimen led to an improvement (complete remission) in 58.9% of the cases. Low-grade metabolic activity was associated with a significant increased risk of worsening/flare at the subsequent PET examination (RR 5.29[1.87-16.11], p=0.002). <h3>Conclusion:</h3> Low-grade vascular inflammation at PET examination is a common feature in LVV treated patients, especially GCA. It is significantly associated with an older age, lower disease duration and clinical remission. However, steroids or immunosuppressants tapering is these patients is associated with an increased risk of worsening/flare. Further research is urgently needed to address this issue. <h3>References:</h3> [1] Dejaco C, et al. Ann Rheum Dis 2018. [2] Meller J, et al. Eur. J. Nucl. Med. Mol. Imaging, 2003. <h3>Disclosure of Interests:</h3> None declared