18 F-Fluorodeoxyglucose-Positron Emission Tomography As an Imaging Biomarker in a Prospective, Longitudinal Cohort of Patients With Large Vessel Vasculitis

Abstract

Objective: To assess the clinical value of 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in a prospective cohort of patients with large vessel vasculitis (LVV) and comparator subjects.

Methods: Patients with Takayasu arteritis and giant cell arteritis were studied, along with a comparator group consisting of patients with hyperlipidemia, patients with diseases that mimic LVV, and healthy controls. Participants underwent clinical evaluation and FDG-PET imaging, and patients with LVV underwent serial imaging at 6-month intervals. We calculated sensitivity and specificity of FDG-PET interpretation for distinguishing patients with clinically active LVV from comparator subjects and from patients with disease in clinical remission. A qualitative summary score based on global arterial FDG uptake, the PET Vascular Activity Score (PETVAS), was used to study associations between activity on PET scan and clinical characteristics and to predict relapse.

Results: A total of 170 FDG-PET scans were performed in 115 participants (56 patients with LVV and 59 comparator subjects). FDG-PET distinguished patients with clinically active LVV from comparator subjects with a sensitivity of 85% (95% confidence interval [95% CI] 69, 94) and a specificity of 83% (95% CI 71, 91). FDG-PET scans were interpreted as active vasculitis in most patients with LVV in clinical remission (41 of 71 [58%]). Clinical disease activity status, disease duration, body mass index, and glucocorticoid use were independently associated with activity on PET scan. Among patients who underwent PET during clinical remission, future clinical relapse was more common in patients with a high PETVAS than in those with a low PETVAS (55% versus 11%; P = 0.03) over a median follow-up period of 15 months.

Conclusion: FDG-PET provides information about vascular inflammation that is complementary to, and distinct from, clinical assessment in LVV. FDG-PET scan activity during clinical remission was associated with future clinical relapse.

© 2017, American College of Rheumatology.

Figures

Figure 1

Qualitative Summary Score of Global Arterial FDG Uptake (PETVAS). A, Mean qualitative scores by arterial region in patients with large vessel vasculitis (LVV) versus a composite disease comparator group. B, Comparison of mean summary score of FDG uptake in 9 arterial territories (PETVAS) in patients with a PET scan interpreted as inactive versus active vasculitis. C, Comparison of PETVAS in patients with giant cell arteritis (GCA), Takayasu’s arteritis (TAK), and disease comparator groups. D, Comparison of PETVAS in patients with GCA and TAK stratified by clinically determined disease activity status. E, Receiver Operating Characteristic Curve of the performance characteristics of PETVAS to differentiate clinically active LVV from LVV in clinical remission. Results in A and B are analyzed by two-tailed student t test. Results in C and D are presented as means with standard error margin and analyzed by one-way ANOVA with post hoc Tukey’s multiple comparison’s test. * p <0.05; ** p<0.01; *** p<0.001; **** p<0.0001. ns = not significant.

Figure 2

Clinical value of FDG-PET findings. A, Global summary score of arterial FDG (PETVAS) calculated in patients with large vessel vasculitis (LVV) during clinical remission predicts future clinical relapse. Patients with high PETVAS (≥ 20) were significantly more likely to relapse than patients with lower PETVAS (< 20) [6/11 (45%) vs 3/28 (15%); p=0.03]. B, PET-CT obtained in a patient with giant cell arteritis during clinical remission (disease duration=3 years, taking prednisone 2.5mg every other day) shows severe FDG uptake throughout the aorta and branch vessels (left panel, white arrows). Patient experienced disease relapse (mesenteric ischemia, fatigue, newly elevated acute phase reactants) one month after the baseline scan and was treated with methotrexate and tapered glucocorticoids with improvement of arterial FDG uptake (right panel, white arrows). C, Patient with GCA in apparent clinical remission (disease duration = 1 year, taking prednisone 7mg per day) had severe FDG arterial uptake in the aorta and branch vessels with normal inflammatory markers. Upon further reduction of daily prednisone to 3mg per day over the subsequent 6 months, the patient experienced clinical relapse (polymyalgia rheumatica, fatigue, elevated acute phase reactants) requiring additional therapy. D, A temporal artery biopsy performed in a patient with GCA during clinical remission with FDG-PET CT suggestive of active vasculitis demonstrated transmural inflammation with giant cells (inset).