18F-sodium fluoride PET-CT visualizes bone formation in psoriatic arthritis patients: Study

Psoriatic arthritis is an inflammatory and chronic musculoskeletal disease linked with psoriasis and several musculoskeletal manifestations, particularly enthesitis, a painful inflammation at the site where ligaments or tendons attach to bone. The formation of new bone can accompany enthesitis activity in PsA.

Bone formation is associated with psoriatic arthritis, and positron emission tomography through an F-18 NaF tracer may enable a sensitive depiction of disease activity. Jerney de Jongh, Amsterdam UMC, Amsterdam, the Netherlands, and colleagues primarily aimed to determine the practicality of whole-body 18F-NaF PET-CT in clinically active patients with psoriatic arthritis to depict new bone formation, which reflects disease activity at peripheral joints and entheses. Secondly, they aimed to describe findings on 18F-sodium fluoride in the axial skeleton.

For this purpose, the researchers included sixteen patients with PsA fulfilling Classification criteria for Psoriatic arthritis (CASPAR) criteria or clinical PsA diagnosis according to a rheumatologist and with ≥ 1 clinically active enthesitis site.

A whole-body 18F-NaF PET-CT scan was performed on each patient. The researchers scored all scans for PET-positive lesions at enthesis sites, peripheral joints, and the spine. Assessment of clinical disease activity was done by swollen/tender joint count 44, enthesitis as per the MASES (Maastricht Ankylosing Spondylitis Enthesitis Score; range 0-13) and SPARCC (Spondyloarthritis Research Consortium of Canada (SPARCC; range 0-16).

The study demonstrated the following findings:

• One hundred nine joints showed PET enhancement out of 1088 evaluated joints, primarily in the metatarsal and interphalangeal joints of the feet (12.9%) and the distal interphalangeal joints of the hands (12.9%).
• The authors found PET positivity at 44/464 enthesis sites, mainly at the quadriceps tendon insertion (10/44, 22.7%) and patella tendon insertion (11/44, 25%)
• 18.2% and 29.5% were clinically positive of the PET-positive joints and enthesis sites; 81.8% and 70.5% of the PET-positive joints and entheses were clinically asymptomatic.
• The researchers observed ≥ 1 axial PET-positive lesion in 11 patients, mainly in the cervical spine.

"18F-NaF PET-CT scans can visualize the formation of new bone, indicating local PsA activity, at all peripheral disease activity sites and perhaps in the axial skeleton," the authors wrote.

"18F-NaF PET-CT may add information to the assessment of clinical disease activity, indicated by a high number of clinically negative, PET-positive sites in addition to concordant findings," they concluded.

Reference:

de Jongh, J., Hemke, R., Zwezerijnen, G.J.C. et al. 18F-sodium fluoride PET-CT visualizes both axial and peripheral new bone formation in psoriatic arthritis patients. Eur J Nucl Med Mol Imaging (2022). https://doi.org/10.1007/s00259-022-06035-w