FDG Uptake in Large-Vessel Giant Cell Arteritis After Short-term, High-Dose Steroid Treatment

Giant cell arteritis (GCA) affects large and medium sized vessels. Large vessel-GCA (LV-GCA) affecting aorta and/or its main branches is seen a) together with temporal arteritis (AT-GCA), b) as isolated LV-GCA but also c) with polymyalgia rheumatica. There is a risk of vision loss and cerebral thromboembolic events or great vessel injury in GCA. With delayed or inadequate treatment mortality and morbidity increases. This highlights the need of fast diagnosis and early treatment. The cornerstone in the diagnosis of GCA is a positive temporal artery biopsy. Patients with LV-GCA have more general, but less cephalic symptoms than patients with AT-GCA. Also, biopsy from large vessels can rarely be done and only 50% have a positive temporal artery biopsy (TAB). Hence, diagnosis often rely on imaging. Fluorine-18-fluorodeoxyglucose positron-emission tomography (FDG PET)/CT has shown high diagnostic sensitivity and specificity and is believed to be superior to other imaging modalities in the diagnosis of LV-GCA . The impact of FDG PET/CT in the management of LV-GCA has been evaluated and has shown to increase the diagnostic accuracy in a significant proportion of patients. However, studies have indicated a lower sensitivity in steroid treated patients. The aim of this study, was to evaluate the effect of steroid treatment on large-vessel FDG uptake in new-onset, treatment-naive LV-GCA by repetitive FDG PET/CT pre- and post therapeutic. With insights into the diagnostic capabilities after treatment is initiated, the possibility of timely treatment and confident diagnostic work up will improve.