Complete PET/CT extinction and subsequent risk of aortic dilation in patients with giant cell arteritis-related large vessel vasculitis treated with tocilizumab.

Clinical remission and complete metabolic response on PET/CT were achieved in 76% of patients with GCA-related LVV treated with tocilizumab.

• 91 patients were included (64 women (70%), median age: 69 (54-83) years) in this retrospective multicentre study.
• 69 patients (76%) achieved both clinical remission and complete metabolic response on repeated PET/CT.
• Complete metabolic response was defined as grade 0 or 1 on the visual vascular to liver FDG uptake grading scale.
• All patients had GCA-related LVV demonstrated on PET/CT and were treated with tocilizumab, undergoing at least one repeated PET/CT.

Among patients achieving complete metabolic response, 30 had discontinued all GCA treatments without relapse after more than 12 months of follow-up post negative PET/CT.

• Of the 69 patients with complete metabolic response, 30 had discontinued all GCA treatments and had not relapsed after >12 months of follow-up post negative PET/CT.
• The remaining 39 patients were still treated or had <12 months of follow-up after the negative PET/CT.
• This subgroup analysis suggests a potential for durable remission after tocilizumab discontinuation in a subset of patients.

13% of patients experienced a relapse of LVV on a third PET/CT within 12 months after tocilizumab discontinuation.

• 13 patients (14%) experienced a relapse of LVV on a third PET/CT within 12 months after TCZ discontinuation.
• Relapse was identified by imaging (third PET/CT) rather than clinical criteria alone.
• This finding indicates that a minority of patients who achieve metabolic response subsequently relapse after stopping tocilizumab.

Complete and persisting PET/CT extinction was associated with a significantly lower risk of aortic dilation during follow-up.

• Aortic dilation occurred in 1 (1%) patient with complete metabolic extinction compared with 4 (18%) patients who did not show complete and persisting PET/CT extinction.
• The difference was statistically significant (p=0.006 by log-rank test).
• This association suggests that persistent vascular inflammation, as detected by PET/CT, may be a risk factor for aortic dilation.
• The finding implies that achieving and maintaining complete metabolic response may reduce the subsequent risk of aortic dilation.