Total lesion glycolysis outperforms visual total vascular score on 18F-FDG-PET/CT as biomarker in giant cell arteritis

To investigate the potential of quantified total arterial 2-deoxy-2-[ 18 F]fluoro-D-glucose ([ 18 F]FDG) positron emission tomography (PET) uptake to monitor and predict disease activity in patients with giant cell arteritis (GCA). All GCA patients enrolled in a prospective cohort with at least one [ 18 F]FDG PET/CT during their disease course were included in this study. Arterial [ 18 F]FDG uptake was assessed using two parameters, the (visual) total vascular score (TVS) and the (quantitative) total lesion glycolysis (TLG). Differences in TVS and TLG between patients in relapse and remission and the diagnostic performance were evaluated. Associations of TLG and TVS with the time to sustained glucocorticoid-free (GC-free) remission and time to relapse were determined. Sixty-four patients with a total of 121 (51 baseline and 70 follow-up) [ 18 F]FDG PET/CT scans were included. The TLG was significantly higher in patients during relapse than in remission ( P = 0.004). TLG showed moderate performance to differentiate patients in relapse from patients in remission (AUC 0.74, P = 0.004). No differences in TVS were found ( P = 0.37) and TVS could not distinguish between these groups (AUC 0.54, P = 0.66). Patients with high TLG at baseline reached GC-free remission earlier than patients with lower TLG (Logrank test for trend P = 0.04). Measuring arterial [ 18 F]FDG uptake using TLG may distinguish between relapse and remission in GCA patients. Higher TLG at baseline was associated with shorter time to GC-free remission. Standard visual assessment performed poorly on both analyses. These findings support the potential of TLG as a new biomarker to monitor and predict GCA disease activity.