Exploring total inflammatory vascular volume as a diagnostic and prognostic biomarker in giant cell arteritis

Abstract

Objectives The objectives of this study were to investigate the role of total inflammation vascular volume (TIVV), a novel quantitative parameter obtained from 18-fluorodeoxyglucose (18F-FDG) PET/CT, in assessing disease activity and predicting relapses and aortic dilatation in patients with large-vessel (LV)-GCA. Methods This retrospective analysis included PET/CT scans from the TOPAZIO study. Patients with active LV-GCA were enrolled and treated with tocilizumab monotherapy for 52 weeks, preceded by three boluses of i.v. methylprednisone. PET/CT scans were performed at baseline and at weeks 24, 52 and 78. TIVV was calculated using a semiautomatic approach, while total inflammation glycolytic volume (TIGV) was obtained by multiplying TIVV by the mean standardized uptake value (SUVmean). Visual assessment was performed, and PET vascular activity score (PETVAS) and total vascular score (TVS) were calculated. Results Eighteen patients with a total of 61 PET scans were included. TIVV and TIGV were strongly associated with active disease, with odds ratios (ORs) of 4.74 (95% CI 1.23-18.2) and 5.45 (95% CI 1.36-21.8), respectively, whereas PETVAS and TVS showed moderate associations (OR 2.16; 95% CI 0.87-5.33 and 1.86; 95% CI 0.76-4.52, respectively). Over a median follow-up of 117 weeks, 10 events occurred. The Cox proportional hazard model showed strong associations of TIVV and TIGV with time to relapse or aortic dilatation, with hazard ratios (HRs) of 2.50 (95% CI 1.07-5.84) and 2.23 (95% CI 1.04-4.82), respectively. PETVAS and TVS exhibited a weaker association with prognosis. Conclusion TIVV and TIGV showed superior diagnostic and prognostic performance compared with conventional PET parameters, underscoring the importance of inflammation volume in evaluating disease activity in LV-GCA.