Vascular Uptake on (18)F-FDG PET/CT During the Clinically Inactive State of Takayasu Arteritis Is Associated with a Higher Risk of Relapse

PURPOSE: To evaluate whether vascular uptake on (18)F-fluorodeoxyglucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) during the clinically inactive state of Takayasu arteritis (TAK) is associated with disease relapse. MATERIALS AND METHODS: Patients with TAK who underwent (18)F-FDG PET/CT during the clinically inactive state of the disease between 2006 and 2019 were included. Clinically inactive disease was defined as a status not fulfilling the National Institutes of Health (NIH) criteria for active disease in TAK. Relapse was defined as recurrence of clinically active disease after a clinically inactive period, requiring change in the treatment regimen. Vascular uptake on (18)F-FDG PET/CT was assessed using target/background ratio (TBR), calculated as arterial maximum standardized uptake value (SUV)/mean SUV in venous blood pool. Multivariable Cox regression analysis was performed to identify factors associated with relapse. RESULTS: A total of 33 patients with clinically inactive TAK were included. During a median observation period of 4.5 (0.9–8.1) years, relapse occurred in 9 (27.3%) patients at median 1.3 (0.7–6.9) years. Notably, TBR [1.5 (1.3–1.8) vs. 1.3 (1.1–1.4), p=0.044] was significantly higher in patients who relapsed than in those who did not. On multivariable Cox regression analysis, the presence of NIH criterion 2 [adjusted hazard ratio (HR): 7.044 (1.424–34.855), p=0.017] and TBR [adjusted HR: 11.533 (1.053–126.282), p=0.045] were significantly associated with an increased risk of relapse. CONCLUSION: Vascular uptake on (18)F-FDG PET/CT and the presence of NIH criterion 2 are associated with future relapse in patients with clinically inactive TAK.