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Fibroblast activation protein inhibitor (FAPI) scans use positron emission tomography (PET) to show where a tracer collects in the body. They are different from treatments aimed at the same target. This guide explains both approaches and how to prepare.
Your specialist can explain why a scan or treatment is being considered, what is known for your cancer type and what remains uncertain.
FAPI PET: imaging
FAPI is a tracer, a small amount of radioactive medicine used for imaging. It attaches to fibroblast activation protein (FAP), found on activated support cells around many tumours and on some tumour cells. The scan shows where the tracer collects.
Healing, scarring and inflammation can also show up. Your team interprets the scan alongside your medical history, other images and any biopsy results.
Why might this scan help?
FAPI may provide useful information in selected situations. It is not a routine replacement for every other scan, and a clearer image does not necessarily mean a better treatment decision.
A useful question is: “What could this scan tell us that my existing tests cannot, and how might that change my care?”
Preparing for your scan
For the FAPI tracer itself, fasting or changing diabetes medicines is generally not needed. Separate instructions may apply if you also need contrast dye to make a computed tomography (CT) scan clearer, sedation (medicine to relax you or make you drowsy), or another procedure. Confirm your appointment instructions and follow the team’s medicine advice.
Tell the team about recent surgery, inflammation, scarring, pregnancy or breastfeeding and any difficulty lying still. Follow the centre's tracer-specific instructions about drinking fluids and close contact after the scan.
FAP-targeted therapy: treatment
A medicine that attaches to FAP can carry a radioactive form of an element, such as lutetium-177. The aim is to deliver treatment radiation to tissue in and around the tumour.
FAP-targeted treatments are experimental and are still being studied. Their possible benefits and risks depend on the exact medicine and cancer type. Your team will explain what the available evidence means for your care.
Does a positive scan mean treatment will work?
A scan helps show where a tracer goes. For treatment to help, the medicine also needs to stay long enough to deliver useful radiation while limiting exposure to healthy organs. A positive scan alone cannot tell us whether treatment will be suitable or effective.
Making a decision together
Your specialist can help you weigh the possible benefit, uncertainties and established alternatives. Before deciding, ask:
- What benefit might this offer for my cancer, and what is still uncertain?
- Is this treatment approved for my situation?
- What will treatment, monitoring and follow-up involve, including the costs?
You can take time to understand the answers and involve a caregiver in the discussion.
Preparing and planning aftercare
Your team will give you written instructions for the exact treatment you receive. These cover medicines, blood tests, pregnancy and breastfeeding, contraception (preventing pregnancy), personal care, sleeping, close contact and travel. The precautions and their duration depend on the medicine.
Discuss any practical difficulties before treatment, such as caring for children or needing help with personal care. Confirm who will manage side effects, who will review your results and who to contact outside working hours.
Frequently asked questions
Do I need to fast before a FAPI scan?
Usually not for the tracer itself. Check your appointment letter because other parts of the visit, such as sedation, may need different preparation. Follow the team’s advice about medicines and fluids.
What happens during the scan?
The tracer is given through a small injection into a vein. You wait while it moves through the body, then lie on the scanner bed while images are taken. Staff can see and hear you. Tell them beforehand if pain or anxiety makes lying still difficult.
Can I go home after the scan?
Most people can go home afterwards. Staff will explain any temporary contact precautions and when to expect your results. If you have sedation, arrange an escort and follow the driving instructions. A treatment appointment may involve a longer stay and different precautions.
Sources and further reading
- Hope et al. — SNMMI/EANM guideline for fibroblast activation protein PET (2025; online 2024)
- IAEA — Radiation Protection and Safety in Medical Uses of Ionizing Radiation: release after radionuclide therapy
- LuMIERE phase I trial — Lutetium-177–FAP-2286 in advanced solid tumours (2026)
- First-in-human lutetium-177–FAPI-XT dose-escalation study (2025)
- NCI — Radiopharmaceutical therapy research
Medically reviewed and approved by Dr (Prof) Vijay Agarwal
Professor and Lead Consultant – Medical Oncology
