The usefulness of 18F-FDG-PET/CT in detecting musculoskeletal and vascular involvement in patients with polymyalgia rheumatica receiving glucocorticoids.

Objective: Fluorine-18-fluorodeoxyglucose (18F-FDG) PET/CT is a promising diagnostic tool for polymyalgia rheumatica (PMR) and large vessel vasculitis (LVV). PET/CT performance is recommended before the onset of steroid therapy because glucocorticoids (GC) may decrease the intensity of FDG uptake. However, this is not always possible in clinical practice. Our aim was to assess if PET/CT could be also useful to detect musculoskeletal and vascular involvement in patients receiving GC.

Methods: Single-center study of patients with PMR diagnosis based on 2012 EULAR/ACR criteria who underwent a PET/CT scan due to LVV suspicion. We compared the musculoskeletal and vascular FDG uptake between two groups: (a) steroid-naïve and (b) steroid-resistant patients. A sub-analysis was conducted in patients who were receiving GC to discern if the cumulative prednisone dose influences the FDG uptake.

Results: We evaluated 75 patients (27 men/ 48 women); mean age±SD: 68.2 ± 10.7 years. PET/CT was performed in 14 steroid-naïve and 61 steroid-resistant patients. Patients under GC had received a median cumulative prednisone dose of 1.8 [0.6-3.9] g. The pattern of musculoskeletal FDG uptake was similar in steroid-naïve and steroid-resistant patients. FDG uptake in the vessel wall was more frequently detected in steroid-naïve patients. However, PET/ CT was also useful to detect LVV in 62.3 % of the patients who were receiving GC. The percentage of patients who had positive PET/CT scans tended to decrease with higher cumulative prednisone doses.

Conclusion: Even though GC therapy may decrease the 18-FDG uptake, PET/CT continues to be a useful tool to detect musculoskeletal and LVV involvement in PMR.