Semiquantitative 18F-FDG PET/CT in the evaluation and management of patients with polymyalgia rheumatica and suspicion of associated aortitis.

Objectives Polymyalgia rheumatica (PMR) may present as an isolated entity or associated to giant cell arteritis (GCA) and some authors consider both entities as different manifestations of the same process. Patients with PMR and concomitant GCA frequently need increased doses of steroids or immunosuppressive drugs. Our objectives were to evaluate the usefulness of 18F-FDG PET/CT in the diagnosis of aortitis associated to PMR and its impact in the management of these patients.

Methods This study included 37 patients (24 women and 13 men, mean age: 68.1±9.9 y.) diagnosed with polymyalgia rheumatica and suspicion of associated aortitis submitted for 18F-FDG PET/CT scan. 18F-FDG PET/CT scan was obtained 180’ after 18F-FDG injection. A semiquantitative analysis of images based on the target (aortic wall) to background (aortic blood pool) ratio (TBR) was performed. A final diagnosis of aortitis was established in 21 out of the 37 patients (56.76%).

Results The mean TBR was 1.63±0.27 (1.33-2.52) for the 21 patients with a diagnosis of aortitis and 1.22±0.06 (1.11-1.34) for the 16 patients without aortitis. The difference between both groups of patients was statistically significant (p<0.0001). ROC analysis revealed that the highest sensitivity (95.24%) and specificity (100%) was obtained for a 1.34 TBR cut-off (area under the curve = 0.997). 18F-FDG PET/CT findings led to a change in the treatment in 17 out of the 21 patients with a diagnosis of aortitis (80.95%).

Conclusions 18F-FDG PET/CT using a semiquantitative analysis was a useful tool in identifying patients with aortitis associated to PMR. The detection of aortic inflammation by 18F-FDG PET/CT had an important impact and led to a change of treatment in 80.95% of these patients.