Comparison of Diagnostic Performance, Semiquantitative Analysis, and Staging Performance of [18F]FAPI-42 and 2-[18F]FDG PET/CT in Lymph Node Metastases

Abstract Background This study was to compare the diagnostic performance, semiquantitative analysis, and staging performance of [ 18 F]-labelled fibroblast activation protein inhibitor ([ 18 F]FAPI-42) and 2-[ 18 F]fluoro-2-deoxy-D-glucose(2-[ 18 F]FDG) PET/CT in lymph node (LN) metastases. Methods From the detection of metastatic LNs, the semiquantitative value of the LN metastases, and the evaluation of N staging, a retrospective analysis of 56 patients diagnosed with LNs metastases who underwent [ 18 F]FAPI-42 and 2-[ 18 F]FDG PET/CT scans within a week for staging or restaging was performed. We analyzed, and compared the diagnostic performance and SUV max of primary tumors and recurrent lesions, as well as the SUV max , TBR, and diagnostic performance of metastatic LNs between [ 18 F]FAPI-42 and 2-[ 18 F]FDG PET/CT. Results A total of 216 metastatic LNs from 56 patients were detected and semi-quantitatively analyzed. Compared to 2-[ 18 F]FDG PET/CT, [ 18 F]FAPI-42 PET/CT presented a better diagnostic performance based on patients (98.2% vs. 92.9%, P = 0.364), based on lesions (87.5% vs. 78.7%, P = 0.015). Regarding semiquantitative analysis, the SUV max of LNs metastases on [ 18 F]FAPI-42 PET/CT presented higher uptake than that on 2-[ 18 F]FDG PET/CT (SUV max 5.0 vs. 3.9, P = 0.002). For differentiating metastatic LNs to normal LNs, the SUV max of [ 18 F]FAPI-42 in metastatic LNs was significantly higher in the non-metastatic LNs (SUV max , 5.0 vs. 1.2, P < 0.001). Comparing the management of N staging between two tracers, [ 18 F]FAPI-42 estimated precisely more patients than 2-[ 18 F]FDG PET/CT (83.9% vs. 78.4%, P = 0.468). Conclusion [ 18 F]FAPI-42 PET/CT showed superior diagnostic performance, the quantitative capability of metastatic LNs, and the management of N staging in patients with cancers compared to 2-[ 18 F]FDG PET/CT.