[18F]FAPI-42 PET imaging in cancer patients: optimal acquisition time, biodistribution, and comparison with [68Ga]Ga-FAPI-04

Authors：Hu, Kongzhen; Wang, Lijuan; Wu, Hubing; Huang, Shun; Tian, Ying; Wang, Qiaoyu; Xiao, Caixia; Han, Yanjiang^*; Tang, Ganghua^*

Source：European Journal of Nuclear Medicine and Molecular Imaging, 2022, 49(8): 2833-2843.

DOI：10.1007/s00259-021-05646-z

• Fibroblast activation protein
• [F-18]FAPI-42
• [Ga-68]Ga-FAPI-04
• PET
• CT

Purpose [F-18]FAPI-42 is a new fibroblast activation protein (FAP)-specific tracer used for cancer imaging. Here, we describe the optimal acquisition time and in vivo evaluation of [F-18]FAPI-42 and compared intra-individual biodistribution, tumor uptake, and detection ability to [Ga-68]Ga-FAPI-04. Methods A total of 22 patients with various types of cancer received [F-18]FAPI-42 whole-body positron emission tomography/computed tomography (PET/CT). Among them, 4 patients underwent PET/CT scans, including an early dynamic 20-min, static 1-h, and static 2-h scans. The in vivo biodistribution in normal organs and tumor uptake were semiquantitatively evaluated using the standardized uptake value (SUV) and tumor-to-background ratio (TBR). Furthermore, both [F-18]FAPI-42 and [Ga-68]Ga-FAPI-04 PET/CT were performed in 12 patients to compare biodistribution, tumor uptake, and tumor detection ability. Results [F-18]FAPI-42 uptake in the tumors was rapid and reached a high level with an average SUVmax of 15.8 at 18 min, which stayed at a similarly high level to 2 h. The optimal image acquisition time for [F-18]FAPI-42 was determined to be 1 h postinjection. For tumor detection, [F-18]FAPI-42 had a high uptake and could be clearly visualized in the lesions. Compared to [Ga-68]Ga-FAPI-04, [F-18]FAPI-42 had the same detectability for 144 positive lesions. In addition, [F-18]FAPI-42 showed a higher SUVmax in liver and bone lesions (P < 0.05) and higher TBRs in liver, bone, lymph node, pleura, and peritoneal lesions (all P < 0.05). Conclusion The present study demonstrates that the optimal image acquisition time of [F-18]FAPI-42 is 1 h postinjection and that [F-18]FAPI-42 exhibits comparable lesion detectability to [Ga-68]Ga-FAPI-04.

• Institution
  1; 南方医科大学