Fig. 2.

Longitudinal change in ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) activity during tocilizumab treatment

Patients who underwent multiple FDG-PET scans during tocilizumab treatment, continued to have reduction in PETVAS (median, IQR) over a two-year treatment period (A). Of the six patients who discontinued tocilizumab, five had worsening FDG-PET activity on subsequent imaging studies, and two patients experienced a clinical relapse in disease activity (red) (B). Representative FDG-PET scans during tocilizumab treatment (C) and post-tocilizumab treatment (D) are shown in a patient with biopsy-proven GCA treated with tocilizumab. While on treatment, there was minimal FDG uptake throughout the large arteries seen on whole-body and axial views (C). He discontinued tocilizumab after 18 months of therapy due to established clinical remission and subsequently developed fatigue, bilateral arm claudication, and elevations in acute phase reactants (ESR 28 and CRP 10.7 mg/L). A repeat FDG-PET scan off tocilizumab showed increased uptake in the large arteries on whole-body (red arrows) and axial views (blue arrows) (D). IQR: interquartile range; PETVAS: PET vascular activity score; TCZ: tocilizumab.