Comparison of 68Ga-DOTA-FAPI-04 and 18F-FDG PET/CT in Patients With SAPHO Syndrome

Abstract

Purpose Synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO) syndrome is a rare inflammatory disorder of bone, joints, and skin, with various stages of bone lesions including inflammation and bone marrow fibrosis. Because the inflammation-induced fibrosis and bone marrow fibrosis are important features in SAPHO syndrome, we undertook a prospective investigation to evaluate whether PET/CT with 68Ga-DOTA-FAPI-04, a novel PET agent targeting fibroblast activation protein, was useful in the evaluation of the patients with SAPHO syndrome. Patients and Methods 68Ga-DOTA-FAPI-04 PET/CT was performed on a cohort of 21 patients with known SAPHO syndrome. All patients underwent 68Ga-DOTA-FAPI-04 and 18F-FDG PET/CT on 2 consecutive days. The positive rates of the PET/CT scans at the sites of the osteoarticular symptom, the uptake values, and agreement with clinical osteoarticular symptom were compared. Results A total of 38 sites of involvement were detected. 18F-FDG PET/CT revealed 28 lesions. In contrast, 68Ga-DOTA-FAPI-04 PET/CT detected not only all lesions shown on 18F-FDG PET/CT but additional 10 lesions. 68Ga-DOTA-FAPI-04 scan also demonstrated significantly higher uptake and target-to-background ratio than 18F-FDG studies in the skeletal involvements. The agreement between 68Ga-DOTA-FAPI-04–positive lesions and current osteoarticular lesions was substantial (κ = 0.79, P < 0.001), whereas 18F-FDG had low to moderate agreement with clinical symptoms (κ = 0.52, P < 0.001). Conclusions 68Ga-DOTA-FAPI-04 has potential as a promising imaging agent for the evaluation of SAPHO syndrome.