Prospective Comparison of 68Ga-FAPI versus 18F-FDG PET/CT for Tumor Staging in Biliary Tract Cancers

Background: Gallium 68-labeled fibroblast-activation protein inhibitor (Ga-68-FAPI), an imaging agent for detecting tumors, represents a promising alternative to fluorine 18 fluorodeoxyglucose (F-18-FDG). Purpose: To compare the potential efficacy of Ga-68-FAPI PET/CT with that of F-18-FDG PET/CT for detecting primary tumor and nodal and distant metastases in biliary tract cancer (BTC) and to explore the impact (tumor staging) of Ga-68-FAPI compared with F-18-FDG on clinical management of BTC. Materials and Methods: This single-center prospective clinical study was performed at the Affiliated Hospital of Southwest Medical University between June 2020 and June 2021. Participants with BTC underwent both Ga-68-FAPI and F-18-FDG PET/CT. Histopathologic examination, morphologic imaging, and/or follow-up imaging served as the reference standard. The maximum standardized uptake value (SUVmax) of the primary tumor and nodal and distant metastases between F-18-FDG and Ga-68-FAPI PET/CT were compared using the paired-sample t test. Results: Eighteen participants with primary or recurrent BTC were evaluated (mean age, 61 years +/- 10 [SD]). The sensitivity of Ga-68-FAPI PET/CT was higher than that of F-18-FDG PET/CT for detecting primary tumors (16 of 16 [100%] vs 13 of 16 [81%]), nodal metastases (41 of 42 [98%] vs 35 of 42 [83%]), and distant metastases (99 of 99 [100%] vs 78 of 99 [79%]). Ga-68-FAPI PET/CT resulted in new oncologic findings in 10 of 18 participants and upgraded tumor staging or restaging in five of 18 participants compared with F-18-FDG PET/CT. Ga-68-FAPI PET/CT demonstrated higher sensitivity than F-18-FDG PET/CT in inflammatory processes secondary to tumor-related obstruction (seven of eight [88%] vs one of eight [13%]). Ga-68-FAPI showed lower average SUVmax in inflammatory processes than in oncologic lesions (4.9 +/- 2.6 vs 10.0 +/- 4.6, respectively; P = .003). Conclusion: Gallium 68-labeled fibroblast-activation protein inhibitor PET/CT for tumor staging showed potential for more accurate staging of biliary tract cancer, thereby improving treatment decision making. (c) RSNA, 2022

Automated summary

Ga-68-FAPI PET/CT showed higher sensitivity than F-18-FDG PET/CT in detecting primary tumors, nodal metastases, and distant metastases in biliary tract cancer. Ga-68-FAPI PET/CT demonstrated higher sensitivity in inflammatory processes secondary to tumor-related obstruction. The study results suggest that Gallium 68-labeled fibroblast-activation protein inhibitor PET/CT may provide more accurate staging information in biliary tract cancer and improve treatment decision making.