Prognostic factors in giant cell arteritis associated aortitis with PET/CT and CT angiography at diagnosis

Background: Prognosis data on giant-cell arteritis (GCA)-associated aortitis are scarce and heterogeneous. The aim of this study was to compare the relapses of patients with GCA-associated aortitis according to the presence of aortitis on CT-angiography (CTA) and/or on FDG-PET/CT. Methods: This multicenter study included GCA patients with aortitis at diagnosis; each case underwent both CTA and FDG-PET/CT at diagnosis. A centralized review of image was performed and identified patients with both CTA and FDG-PET/CT positive for aortitis (Ao-CTA+/PET+); patients with positive FDG-PET/CT but negative CTA for aortitis (Ao-CTA-/PET+), and patients solely positive on CTA. Results: Eighty-two patients were included with 62 (77%) of female sex. Mean age was 67 +/- 8 years; 64 patients (78%) were in the Ao-CTA+/PET+ group; 17 (22%) in the Ao-CTA-/PET+ group and 1 had aortitis only on CTA. Overall, 51 (62%) patients had at least one relapse during follow-up: 45/64 (70%) in the Ao-CTA+/PET+ group and 5/17 (29%) in the Ao-CTA-/PET+ group (log rank, p = 0.019). In multivariate analysis, aortitis on CTA (Hazard Ratio 2.90, p = 0.03) was associated with an increased risk of relapse. Conclusion: Positivity of both CTA and FDG-PET/CT for GCA-related aortitis was associated with an increased risk of relapse. Aortic wall thickening on CTA was a risk factor of relapse compared with isolated aortic wall FDG uptake.