Fibroblast Activation Protein–Targeted PET/CT with<sup>68</sup>Ga-FAPI for Imaging IgG4-Related Disease: Comparison to<sup>18</sup>F-FDG PET/CT
Yaping Luo, Qingqing Pan, Huaxia Yang, Linyi Peng, Wen Zhang, Fang Li
Abstract
IgG4-related disease (RD) is characterized by lymphoplasmacytic infiltration enriched in IgG4-positive plasma cells and variable degrees of fibrosis with a characteristic storiform pattern. Since fibrosis is an important feature of IgG4-RD, we performed a prospective cohort study to evaluate the performance of 68 Ga-fibroblast activation protein inhibitor (FAPI), a recently introduced PET agent targeting fibroblast activation protein, in IgG4-RD. Methods: Twenty-six patients with IgG4-RD were recruited. All patients underwent both 68 Ga-FAPI and 18 F-FDG PET/CT. The positive rates of the PET/CT scans in the involved organs and the uptake values were compared. Results: In a total of 136 involved organs in the 26 patients, 68 Ga-FAPI PET/CT additionally detected 18 (13.2%) involved organs in 13 (50.0%) patients, compared with 18 F-FDG PET/CT. 68 Ga-FAPI PET/CT had a higher positive rate than 18 F-FDG PET/CT in detecting involvement in the pancreas, bile duct/ liver, and lacrimal gland. 68 Ga-FAPI also demonstrated significantly higher uptake than 18 F-FDG in the matched disease in the pancreas, bile duct/liver, and salivary gland (P , 0.01). However, lymph node involvement with flip-flop uptake of 18 F-FDG did not accumulate 68 Ga-FAPI. Conclusion: 68 Ga-FAPI might be a promising imaging agent for the assessment of IgG4-RD.