AB0354 FDG-PET-DETECTED LARGE VESSEL VASCULITIS DOES NOT PREDICT DISEASE OUTCOME IN PATIENTS WITH GIANT CELL ARTERITIS AND POLYMYALGIA RHEUMATICA

Background: Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are tightly associated inflammatory conditions of the elderly [1]. Both disorders can exhibit an increased articular and vascular uptake of 18-fluorodeoxyglucose (18-FDG) at positron emission tomography (PET)/computed tomography (CT) scan [2]. Objectives: This study evaluated if large-vessel vasculitis (LVV) detected by PET/CT in patients with PMR and/or cranial GCA had a negative prognostic value. Methods: 108 patients (35 men and 73 women) with a median age of 74 years (range 50-92 years) were prospectively enrolled in our centre over 4 years. PMR was diagnosed by Bird et al. criteria and GCA by the ACR criteria. Six patients died shortly after the first visit (V0) and six were lost at follow-up. Of the remaining 96 patients, 77 were classified as PMR, 6 as GCA and 13 were affected by both diseases. At V0, patients underwent a clinical, laboratory and PET/CT evaluation, and were stratified according to the presence or not of LVV. Follow-up visits were performed every 6 months for a median of 40 months. Disease outcomes were: prednisone (PDN) use and its cumulative dosage, need of methotrexate (MTX), number of relapses, patients’ death, and PMR disease activity score (PMR-DAS). The independent variables were age, sex, disease duration, fever, C-reactive protein (CRP) concentration, platelet count (PLT), presence of cranial GCA, degree of joint and vascular uptake of FDG, and presence of LVV. The predictive role of LVV was tested by multiple regression. Results: LVV was seen in 47 patients (49 %), 31 with PMR, 6 with GCA and 10 with both diseases. Patients with or without LVV did not significantly differ in terms of demographic and laboratory parameters except for a non-significant higher number of PLT in patients with LVV. Clinical and laboratory parameters at V0, stratified per disease and considered together, did not significantly change between PET+ and PET- patients (table 1). Lastly, none of the independent variables, including LVV, could predict disease outcomes. Conclusion: The presence of a PET-detected LVV at diagnosis does not seem a negative prognostic factor in PMR and GCA. As a consequence, routine investigation by PET/CT of patients with PMR and GCA is not indicated to predict disease outcome. References: [1]Dejaco C, Duftner C, Buttgereit F, Matteson EL, Dasgupta B. The spectrum of giant cell arteritis and polymyalgia rheumatica: revisiting the concept of the disease. Rheumatology (Oxford). 2017 Apr 1;56(4):506-515. doi: 10.1093/rheumatology/kew273. PMID: 27481272. [2]Blockmans D, Coudyzer W, Vanderschueren S, Stroobants S, Loeckx D, Heye S et al. Relationship between fluorodeoxyglucose uptake in the large vessels and late aortic diameter in giant cell arteritis. Rheumatology (Oxford). 2008 Aug;47(8):1179-84. doi: 10.1093/rheumatology/ken119. Epub 2008 May 31. PMID: 18515868. Disclosure of Interests: None declared