GLUCOCORTICOIDS, CONVENTIONAL DMARDS AND TOCILIZUMAB DIFFERENTLY AFFECT 18F-FDG PET METABOLIC ACTIVITY IN GIANT CELL ARTERITIS PATIENTS
Authors: Mekinian A. et al.
Imaging techniques such as ultrasound, MRI and PET-CT have replaced biopsy/histology in diagnosing GCA in many centers. The role of 18F-FDG PET in evaluating treatment response, however, has to be defined. The authors evaluate the effect of glucocorticoids (GC), conventional disease modifying anti-rheumatic drugs (cDMARDs) and tocilizumab (TCZ) on metabolic activity of giant cell arteritis (GCA) with extra-cranial involvement.
Consecutive patients with large vessel vasculitis (LVV) were prospectively enrolled if they had at least 2 consecutive 18F-FDG PET-CT scans. GCA patients were compared according to current treatment regimen: GC monotherapy versus cDMARDs (methotrexate, azathioprine) and versus TCZ (administered both subcutaneously and intravenously). For each PET scan the vessel’s metabolic activity was evaluated using the Meller’s grading and the PETVAS score.
The study included 47 patients (age 66, 72.3% female) exposed to a total of 77 treatment regimens (n=37 GC monotherapy, n=26 cDMARDs, n=14 TCZ). A total of 181 PET scan were conducted. Remission rate during the follow-up was 75.7% in GC-treated patients, 69.2% in cDMARDs-treated and 85.7% in TCZ-treated patients (p=0.513). All the treatment led to significant reduction of acute phase reactants. However, significant improvement in PETVAS was observed in TCZ-treated patients only (12 vs 4, p=0.002, ΔPETVAS -66.7%). At the last examination residual signal (Meller 1-2) was observed in 56.8% of GC-treated patients, 57.7% of cDMARDs-treated patients and 64.3% of TCZ treated patients (p=0.884).
The authors conclude that 18F-FDG PET may serve as a tool to monitor response to therapy and, surprisingly, they show a significant difference between different treatment regimens. The fact that residual signals persist is a well-known finding, it has been reported in all imaging techniques in roughly 60% of cases. Unfortunately, the role of imaging techniques regarding early detection of relapse is still unknown.