Background/Purpose: Persistent large-vessel vasculitis (LVV) on PET/CT in giant-cell arteritis (GCA) is associated with a higher risk of aortic dilation. Few data are available on complete metabolic response under treatment (i.e., total extinction of vascular uptakes). This study compared the ability of glucocorticoids (GC) alone and GC + tocilizumab (TCZ) to obtain a complete metabolic response on repetitive PET/CT.

Methods: Through the French Large-Vessel Vasculitis Study Group (GEFA), we retrospectively enrolled all GCA patients who satisfied the following criteria: 1) a LVV was evidenced on PET/CT; 2) all patients were treated either with GC alone or GC+TCZ; and 3) at least a second PET/CT was repeated under the same initial treatment. Patients who received another treatment between the two repeated PET/CT were excluded. Patients who showed a total vascular extinction on repeated PET/CT without LVV relapse during follow-up were considered as a success. Patients with still positive PET/CT or with LVV relapse during follow-up were considered as failures.

Results: A total of 167 patients were enrolled, 76 treated with GC alone and 91 treated with GC + TCZ. Their characteristics at baseline are shown and compared in Table 1. LVV was diagnosed on PET/CT at GCA diagnosis in 66% and 71% (p=ns) of patients in the GC and GC+TCZ groups, respectively. A second PET/CT was repeated at 8 [IQR 25-75, 6–11] months in the GC group and 12 [10–20] months in the GC+TCZ group (p< 0.0001). Under GC alone, 41% of PET/CT showed a total extinction of vascular uptakes versus 76% in the TCZ group (p< 0.0001). Figure 1 shows the proportion of negative PET/CT in the two groups according to the time of control. LVV relapse on a third PET/CT was diagnosed in 5% of patients treated with GC alone and 12% of patients treated with GC+TCZ (p=0.17). At last follow-up, more patients treated with GC+TCZ had discontinued GC (79% vs. 61% in patients treated with GC alone, p=0.009).

Conclusion: This study suggests that the combination of GC+TCZ is more efficient than GC alone to obtain a complete metabolic extinction on repeated PET/CT in GCA-related large vessel vasculitis. A further longitudinal study is required to analyze the impact on the risk of aortic dilation.

Table 1. Comparison of GC alone and GC+TCZ to obtain a PET/CT extinction in GCA-related LVV

Figure 1. Proportion of negative PET/CT in the two groups according to the time of control.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/complete-metabolic-response-on-pet-ct-in-giant-cell-arteritis-related-large-vessel-vasculitis-comparison-of-two-strategies-using-glucocorticoids-or-glucocorticoids-tocilizumab/