Use of 18F-fluorodeoxyglucose positron emission tomography to monitor tocilizumab effect on vascular inflammation in giant cell arteritis

Abstract Objectives To evaluate the time-dependent effects of tocilizumab on vascular inflammation as measured by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) in GCA. Methods Patients with GCA treated with tocilizumab were selected from a prospective, observational cohort. Patients underwent FDG-PET at the baseline visit prior to initiation of tocilizumab and at subsequent follow-up visits performed at 6-month intervals. All imaging findings were interpreted blinded to clinical data. The PET vascular activity score (PETVAS) was used to quantify arterial FDG uptake. Wilcoxon signed rank test was used to compare change in PETVAS between visits. Linear regression was used to determine change in PETVAS over multiple timepoints. Results Twenty-five patients with GCA were included. All patients had physician-determined active vasculitis at the baseline visit by clinical assessment and FDG-PET interpretation. PETVAS was significantly reduced in association with tocilizumab treatment from the baseline to the most recent follow-up visit [24.0 (IQR 22.3–27.0) vs 18.5 (IQR 15.3–23.8); P