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

The proportion of patients with giant cell arteritis (GCA)-related large vessel vasculitis (LVV) treated with tocilizumab (TCZ) who achieve a complete metabolic response on repeated 18 F-fluorodeoxyglucose positron emission tomography (18FDG-PET)-CT (PET/CT) is unknown. We conducted a retrospective multicentre study that enrolled patients with GCA-related LVV demonstrated on PET/CT, who were treated with TCZ and underwent at least one repeated PET/CT. The primary endpoint was the proportion of patients with vascular extinction on repeated PET/CT during or after TCZ treatment (grade 0 or 1 on the visual vascular to liver FDG uptake grading scale). A total of 91 patients (64 women (70%), median age: 69 (54-83) years) were included. Clinical remission and a complete metabolic response on PET/CT were observed in 69 patients (76%). Among these, 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.13 (14%) patients experienced a relapse of LVV on a third PET/CT within 12 months after TCZ discontinuation. During follow-up, an aortic dilation occurred in one (1%) patient with complete metabolic extinction and in four (18%) patients who did not show complete and persisting PET/CT extinction (p=0.006 by log-rank test). This study suggests that TCZ is an interesting therapeutic option for achieving complete metabolic response on PET/CT in patients with GCA-related LVV. The subsequent risk of aortic dilation may be reduced.