FAPI-74 PET/CT Using Either ¹⁸F-AlF or Cold-Kit ⁶⁸Ga Labeling: Biodistribution, Radiation Dosimetry, and Tumor...

Area of Science:

• Nuclear Medicine
• Radiochemistry
• Oncology Imaging

Background:

• Gallium-68 labeled fibroblast activation protein inhibitors (FAPIs) are promising PET tracers but face manufacturing and delivery challenges due to the short half-life of Gallium-68.
• Fluorine-18 labeling offers a longer half-life for improved production and availability, with cold-kit formulations enhancing spontaneous use.
• FAPI-74, a NOTA chelator ligand, is suitable for labeling with both 18F-AlF and 68Ga.

Purpose of the Study:

• To evaluate the in vivo performance of 18F-FAPI-74 as a PET tracer for lung cancer.
• To demonstrate the mechanism of 68Ga-FAPI-74 labeling at ambient temperature.
• To assess the biodistribution, tumor uptake, and radiation dosimetry of both 18F-FAPI-74 and 68Ga-FAPI-74.

Main Methods:

• Ten lung cancer patients underwent PET scans at 10 min, 1 h, and 3 h post-injection of 18F-FAPI-74 (259 ± 26 MBq).
• Semiquantitative evaluation of biodistribution and tumor uptake using SUV.
• Absorbed dose calculations using OLINDA/EXM and QDOSE software; one patient received 68Ga-FAPI-74 (263 MBq).

Main Results:

• Optimal contrast for primary tumors, lymph nodes, and metastases was observed at 1 h post-injection (SUVmax > 10).
• Effective dose for 18F-FAPI-74 was 1.4 ± 0.2 mSv per 100 MBq, and for 68Ga-FAPI-74 it was 1.6 mSv.
• The radiation burden of 18F-FAPI-74 PET/CT is lower than 18F-FDG, and 68Ga-FAPI-74 is comparable to other 68Ga ligands; FAPI PET/CT aided radiotherapy target volume definition.

Conclusions:

• FAPI-74 PET/CT exhibits high contrast and a low radiation burden, supporting diverse clinical applications.
• Centralized production of 18F-FAPI-74 or decentralized cold-kit labeling of 68Ga-FAPI-74 enables flexible routine clinical use.
• FAPI-74 PET/CT is a valuable tool for lung cancer imaging and radiotherapy guidance.