⁶⁸Ga-FAPI PET/CT for Rheumatoid Arthritis: A Prospective Study

Area of Science:

• Nuclear Medicine
• Radiopharmaceuticals
• Rheumatology

Background:

• Rheumatoid arthritis (RA) involves fibroblast-like synoviocyte overexpressing fibroblast activation protein (FAP).
• FAP overexpression in RA presents a potential target for improved disease imaging.
• Current imaging methods may not fully capture the extent of RA joint involvement.

Purpose of the Study:

• To evaluate the efficacy of gallium 68 (⁶⁸Ga)-labeled FAP inhibitor (FAPI) PET/CT in assessing RA joint disease activity.
• To compare the performance of ⁶⁸Ga-FAPI PET/CT with fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/CT in RA patients.

Main Methods:

• Prospective enrollment of 20 participants with RA.
• Dual-tracer PET/CT imaging using both ⁶⁸Ga-FAPI and ¹⁸F-FDG.
• Correlation of imaging-derived variables (PET joint count, PET articular index, SUVmax) with clinical and laboratory disease activity measures.

Main Results:

• ⁶⁸Ga-FAPI PET/CT detected all RA-affected joints identified by both modalities.
• ⁶⁸Ga-FAPI PET/CT identified 6.1% more FAPI-avid joints not detected by ¹⁸F-FDG PET/CT.
• Higher maximum standardized uptake values (SUVmax) were observed with ⁶⁸Ga-FAPI compared to ¹⁸F-FDG (P = .001).
• Both ⁶⁸Ga-FAPI and ¹⁸F-FDG SUVmax correlated positively with C-reactive protein levels.
• ⁶⁸Ga-FAPI PET/CT scores correlated significantly with clinical disease activity and radiographic progression.

Conclusions:

• ⁶⁸Ga-FAPI PET/CT demonstrates superior sensitivity in detecting RA joint involvement compared to ¹⁸F-FDG PET/CT.
• The extent and degree of joint involvement assessed by ⁶⁸Ga-FAPI PET/CT correlate well with clinical and laboratory markers of RA disease activity.
• ⁶⁸Ga-FAPI PET/CT offers a promising advanced imaging approach for evaluating rheumatoid arthritis.