18 F-FDG PET/CT in the follow-up of large-vessel vasculitis: A study of 37 consecutive patients.

OBJECTIVE: 18 F-FDG PET/CT has proved to be of potential value for early diagnosis of large-vessel vasculitis (LVV), which frequently involves the aorta. However, its role in the follow-up of these patients has not been well established. Our aim was to evaluate the contribution of 18 F-FDG PET/CT in this clinical situation.

METHODS: This study included 37 consecutive patients (28 women, 66.5 ± 9.9 years) with an initial 18 F-FDG PET/CT positive for LVV and a mean ± standard deviation follow-up PET/CT of 7.5 ± 2.9 months after the initial scan. A semiquantitative analysis of aortic wall uptake was performed calculating the target-to-background ratio (TBR: aortic wall uptake divided by blood pool uptake). The initial and follow-up TBR as well as the clinical and laboratory outcome were compared.

RESULTS: Overall, the mean TBR decreased from 1.7 ± 0.5 at the initial scan to 1.5 ± 0.3 at the time of follow-up (p = 0.0001). In the 21 patients who experienced clinical improvement following therapy the TBR also decreased from 1.8 ± 0.6 to 1.5 ± 0.3 (p = 0.0002). However, in the other 16 patients, in whom the treating physician considered that there was no clinical improvement following therapy, no statistically significant differences in TBR were found when data from the first and the follow-up PET/CT scans were compared (1.6 ± 0.3 versus 1.5 ± 0.3, p = 0.1416). Patients who experienced clinical improvement following therapy showed a nonstatistically significant higher TBR at the time of disease diagnosis (1.8 ± 0.6 versus 1.6 ± 0.3; p = 0.12).

CONCLUSIONS: The results obtained in the present study highlight the impact of 18 F-FDG PET/CT on the management of patients with LVV.