232. CHANGE IN VASCULAR 18F-FLUORODEOXYGLUCOSE POSITRON EMISSION TOMOGRAPHY ACTIVITY WITH TREATMENT IN LARGE VESSEL VASCULITIS IN RELATION TO CLINICAL AND SEROLOGIC ASSESSMENT

Abstract

Background: Activity in large-vessel vasculitis (LVV) is traditionally assessed by clinical and serological parameters. Imaging assessment, including FDG-PET, may also be useful to monitor LVV. This study aimed to determine if current therapies for LVV impact disease activity as determined by FDG-PET in relationship to clinical, and serologic-based assessments. Methods: Patients with giant cell arteritis (GCA) or Takayasu's arteritis (TAK) were recruited into a prospective, observational cohort. All subjects in this study underwent 2 FDG- Results: Serial assessments were performed in 52 patients with LVV (GCA=31; TAK=21) over 156 visits. Interval treatment changes involved glucocorticoids (n = 46), methotrexate (n = 23), tocilizumab (n = 17), infliximab (n = 7), or another DMARD and/or biologic (n = 10). Increased, decreased, or unchanged therapy was recorded for 36, 23, and 32 visit intervals, respectively. In the increased treatment group, there was significant reduction in disease activity by imaging, clinical, and inflammatory markers (p < 0.01 for each). When treatment was unchanged, PETVAS (p = 0.95); PGA (p = 0.48), CRP (p = 0.57) remained stable. When treatment was decreased, PET activity worsened (p = 0.02); there were no differences in PGA (p = 0.52) or CRP (p = 0.10). Treatment with tocilizumab in GCA (n = 17) and infliximab in TAK (n = 7) resulted in significant improvement in both imaging and clinical assessments of disease activity. Conclusion: This study identified concordant and discordant changes between disease activity measurement by vascular FDG- PET uptake and traditional methods in relationship to treatment. These findings support a need to study the FDG-PET as a potential outcome measure of vascular activity in clinical trials.