Head to head comparison of 18F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging used in diagnosis of autoimmune rheumatic diseases

Abstract

Objectives: The aim of this study was to determine the performance of radionuclide-labeled fibroblast activation protein inhibitors (Al¹⁸F-NOTA-FAPI-04) PET/CT in patients with autoimmune rheumatic diseases (ARDs) and compare it with fluorine-18 (¹⁸F) labeled fluorodeoxyglucose (FDG) imaging.

Methods: Fifty-eight participants with ARDs were prospectively enrolled from April 2022 to February 2024 and underwent dual-tracer PET/CT imaging. For both ¹⁸F-FDG and Al¹⁸F-NOTA-FAPI-04 PET/CT, imaging findings were interpreted and compared. The clinical significance was compared between¹⁸F-FDG PET/CT and Al¹⁸F-NOTA-FAPI-04 PET/CT imaging.

Results: ¹⁸F-FDG imaging was positive in 53 out of 58 cases (91.4%) while Al¹⁸F-NOTA-FAPI-04 imaging was positive in 55 out of 58 cases (94.8%). Overall positive rate of Al¹⁸F-NOTA-FAPI-04 imaging was as high as ¹⁸F-FDG imaging (P = 0.625). ¹⁸F-FDG imaging detected more lesions in lymph node, spleen, and bone marrow. Al¹⁸F-NOTA-FAPI-04 imaging detected more lesions in the lung, muscle, and tendon/ligament. There was no statistical difference of composing ratio of grades of clinical significance between two imaging modalities (χ² = 2.875, P = 0.238). The superior rate of Al¹⁸F-NOTA-FAPI-04 PET/CT imaging was higher than ¹⁸F-FDG imaging (P = 0.020). In subgroup of adult-onset Still's disease, ¹⁸F-FDG imaging showed better performance than Al¹⁸F-NOTA-FAPI-04 imaging. In most of the other subgroup of ARDs, Al¹⁸F-NOTA-FAPI-04 PET/CT imaging overperformed ¹⁸F-FDG imaging.

Conclusion: Both ¹⁸F-FDG and Al¹⁸F-NOTA-FAPI-04 PET/CT imaging have excellent sensitivity in ARDs. The detection capabilities of two tracers varied according to the involving organs of ARDs. In most of ARDs except adult-onset Still's disease, Al¹⁸F-NOTA-FAPI-04 PET/CT imaging overperformed ¹⁸F-FDG imaging. Key Points • ¹⁸F-FDG and Al18F-NOTA-FAPI-04 PET/CT imaging have excellent sensitivity in diagnosing of ARDs. • ¹⁸F-FDG PET/CT imaging detected more lesions in lymph node, spleen, and bone marrow. • ¹⁸F-NOTA-FAPI-04 PET/CT imaging detected more lesions in the lung, muscle, and tendon/ligament. • ¹⁸F-NOTA-FAPI-04 PET/CT imaging overperformed¹⁸F-FDG in most subgroups of ARDs.

Keywords: Fibroblast activation protein alpha; Fluorodeoxyglucose F18; Positron emission tomography; Rheumatic diseases.