Fibroblast Activation Protein Inhibitor (FAPI) PET: A Scoping Review of Emerging Oncologic and Fibroinflammatory...

Area of Science:

• Molecular Imaging
• Radiochemistry
• Oncology
• Immunology

Background:

• Fibroblast Activation Protein (FAP) is expressed on activated mesenchymal cells, including cancer-associated fibroblasts (CAFs) and myofibroblasts in tumor stroma and fibroinflammatory disorders.
• FAPI tracers, labeled with Gallium-68 ([⁶⁸Ga]) or Fluorine-18 ([¹⁸F]), target FAP, providing high contrast for imaging.
• FAP expression is relevant in various cancers and chronic fibroinflammatory conditions like rheumatoid arthritis and organ fibrosis.

Purpose of the Study:

• To summarize advances in fibroblast activation protein inhibitor (FAPI) positron emission tomography (PET) for oncologic and fibroinflammatory diseases.
• To review the current status and future potential of FAPI PET in clinical practice.
• To assess the translational potential and requirements for widespread adoption of FAPI PET.

Main Methods:

• A scoping review was conducted following PRISMA-ScR guidelines.
• Systematic literature search of PubMed and Scopus for publications from January 2018 to February 2026.
• Inclusion of original studies, reviews, guidelines, and case reports on FAPI-targeted PET in human subjects or translational models.

Main Results:

• 256 sources were included, highlighting FAPI PET's high tumor-to-background contrast, especially in desmoplastic cancers.
• FAPI PET shows superior lesion conspicuity over [¹⁸F]FDG in some malignancies and allows a non-fasting workflow.
• FAPI PET is emerging for cardiac fibrosis, pulmonary inflammation, and autoimmune diseases, demonstrating translational potential due to favorable biodistribution, safety, and theranostic flexibility.

Conclusions:

• FAPI PET is a maturing molecular imaging platform targeting activated fibroblasts in oncologic and fibroinflammatory diseases.
• Standardized protocols and ongoing trials support reproducible implementation.
• Widespread clinical adoption requires large-scale validation, reader training, and regulatory approval, which are currently in progress.