FAPI PET-CT: — The Tracer That Finds What FDG Misses

FAPI stands for Fibroblast Activation Protein Inhibitor — it is the radioactive molecule injected before the scan. In many cancers, the tissue surrounding the tumour is rich in cancer-associated fibroblasts that express a protein called FAP. FAPI binds to FAP selectively. Because FAP is present in large amounts on these activated fibroblasts but not significantly in most normal adult tissue, the tracer builds up where the tumour is and gives a low background signal elsewhere. The PET scanner then detects the radiation from the tracer to build an image of where it has accumulated.

FAPI PET-CT tends to give the clearest advantage in cancers where FDG uptake is typically low — most often gastric, pancreatic, biliary tract, peritoneal, and some ovarian cancers, as well as soft tissue sarcomas. It has also been studied in head and neck and breast cancers. How much it helps depends on both the cancer type and your individual tumour. Your oncologist will tell you whether your specific cancer is one where published evidence supports a FAPI scan and whether the result is likely to change your management.

You generally do not need to fast before a FAPI PET-CT, which is a practical difference from FDG. FDG requires fasting to keep blood glucose stable because glucose competes with the tracer for uptake. FAPI works via a different mechanism — binding to a protein, not glucose transport — so fasting is typically not required. The preparation instructions will be given to you by the imaging centre when your scan is booked. Follow those instructions specifically, because protocols can vary between centres.

FAPI does not replace FDG — they answer different questions. FDG remains superior for cancers that are highly metabolically active, including many lymphomas, melanomas and certain lung cancers. FAPI adds value where FDG returns a weak or equivocal signal. Your oncologist may suggest both in some circumstances, or FAPI alone where FDG has already been done and the result was not clear enough. The decision is about which imaging question needs to be answered, not about which tracer is universally better.

FAPI PET-CT is coordinated through CION's partner imaging centres. The indicative cost is ₹23,999 (2026 — confirm at the time of booking, as prices can change). Your treating oncologist at CION will request the scan where appropriate. The scan itself is performed at a partner centre, and results are reviewed as part of your ongoing care at CION. PET-CT is not performed at CION's own centres; CION coordinates with accredited partner imaging facilities.

The evidence is growing and promising, but it is not yet at the same level of maturity as FDG for most cancers. Multiple prospective studies and published research, along with guidance from the European Association of Nuclear Medicine, support FAPI's utility in specific cancer types. It is used clinically at specialist centres in India and internationally. What the evidence does not yet establish clearly is whether detecting additional disease on FAPI changes long-term outcomes — that question is still being studied. Your oncologist can tell you whether the published evidence for your specific cancer type is strong enough to act on.