FAPI PET CT scan is a newer type of nuclear medicine imaging that detects cancers traditional FDG PET CT can miss. Available at select centres in Bangalore (Bengaluru), FAPI PET CT targets fibroblast activation protein (FAP) in the tumour microenvironment rather than glucose metabolism, giving it a different and often complementary view of cancer compared to standard PET CT scans.
What Is FAPI?
FAPI stands for fibroblast activation protein inhibitor. Fibroblast activation protein (FAP) is a molecule found on cancer-associated fibroblasts, which are cells in the tissue surrounding many types of tumours. These fibroblasts are part of the tumour’s microenvironment and play a role in how the cancer grows and spreads.
A FAPI PET CT scan uses a radioactive tracer that binds to FAP. Because FAP is present around many different tumour types, FAPI PET CT has potential applications across a broader range of cancers than some other specialised tracers.
Why FAPI Can Find Cancers That FDG Misses
FDG, the most commonly used PET tracer, works by detecting increased glucose metabolism. Most cancers consume more glucose than normal cells, making them visible on an FDG PET CT. However, some cancers have only modestly increased glucose uptake, which makes them harder to spot against the background of normal tissue.
FAPI works through a completely different mechanism. It targets the fibroblasts around the tumour rather than the tumour cells themselves. This means it can highlight cancers that are metabolically quiet on FDG but still have an active stromal (surrounding tissue) response.
Key Advantages of FAPI Over FDG
| Feature | FDG PET CT | FAPI PET CT |
|---|---|---|
| Mechanism | Targets glucose metabolism | Targets fibroblast activation protein |
| Brain uptake | High background (makes brain tumour detection difficult) | Low background (clearer brain imaging) |
| Liver uptake | Moderate background | Very low background |
| Fasting required | Yes (4-6 hours) | No |
| Diabetic patients | Blood sugar management needed | No glucose-related preparation |
| Scan timing after injection | 60 minutes | 10-60 minutes (varies by protocol) |
| Inflammation false positives | Common | Less frequent |
Low background uptake: Unlike FDG, which shows high uptake in the brain, liver, and urinary tract as part of normal metabolism, FAPI has very low uptake in most normal tissues. This creates cleaner images and makes it easier to spot tumours in areas where FDG creates confusing signals.
Better in certain organs: Tumours in the brain, liver, and biliary tract can be difficult to evaluate with FDG because of high background activity. FAPI often provides clearer contrast in these locations.
No fasting required: Because FAPI does not depend on glucose metabolism, patients do not need to fast before the scan. This can be an advantage for patients with diabetes or those who have difficulty fasting.
Which Cancers Can FAPI PET CT Help With?
Research has shown promising results for FAPI PET CT in several cancer types:
- Pancreatic cancer – where FDG uptake can be variable
- Cholangiocarcinoma (bile duct cancer) – difficult to image with FDG due to liver background
- Gastric cancer – FAPI can detect peritoneal spread more reliably
- Certain sarcomas – soft tissue tumours with strong stromal response
- Some breast cancers – particularly lobular breast cancer, which can be FDG-negative
- Hepatocellular carcinoma (liver cancer) – where FDG is less reliable
- Head and neck cancers – for treatment planning and recurrence detection
FAPI is not a replacement for FDG in all situations. For cancers where FDG performs well, such as lung cancer and lymphoma, FDG remains the standard first-line tracer. FAPI is most valuable when FDG has limitations for a particular cancer type or when additional information is needed. Read a detailed FAPI vs FDG comparison for more on when each tracer is appropriate.
FAPI in Theranostics
Just as PSMA can be used for both imaging and therapy in prostate cancer, FAPI is being explored as a theranostic target. If a FAPI PET CT confirms that a tumour’s microenvironment expresses FAP, a therapeutic version of the FAPI molecule carrying a treatment dose of radiation (such as Lu-177 FAPI) could potentially be used for treatment.
This application is still in the early stages of clinical research, and it is not yet a standard treatment. However, the theranostic potential of FAPI is an active area of investigation that could expand treatment options for several difficult-to-treat cancers.
FAPI PET CT Scan in Bangalore
FAPI PET CT is available at select nuclear medicine centres in Bangalore (Bengaluru). Not all PET CT centres offer this tracer because it requires specific procurement channels and nuclear medicine expertise. When looking for a FAPI PET CT scan in Bengaluru, confirm that the centre has experience with FAPI imaging and that a nuclear medicine physician will interpret the scan.
Dr. Prathap H.J. offers FAPI PET CT scans in Bangalore along with 15+ other specialised tracers including FDG, PSMA, Ga-68 DOTANOC, CXCR4, and Exendin. The centre is located at Ulsoor Road, Bangalore 560042. Contact the clinic to schedule a FAPI PET CT scan or to discuss whether FAPI imaging is appropriate for your case.
Is FAPI PET CT Right for You?
The decision to use FAPI PET CT rather than, or in addition to, FDG PET CT depends on the clinical question being asked. Your oncologist and nuclear medicine physician will consider the type and location of your cancer, what information is needed, and what other imaging has already been done.
If you have been told that your cancer is not clearly visible on FDG PET CT, or if your doctor is looking for additional information to guide treatment, ask whether a FAPI PET CT could be helpful in your situation.
Frequently Asked Questions About FAPI PET CT
Where can I get a FAPI PET CT scan in Bangalore?
FAPI PET CT is available at select nuclear medicine centres in Bangalore (Bengaluru). Dr. Prathap H.J. offers FAPI PET CT scans at Ulsoor Road, Bangalore 560042. Since the FAPI tracer is produced specifically for each appointment, scans are typically scheduled in advance.
Is FAPI PET CT scan available near me in Bengaluru?
Yes, FAPI PET CT scan is available in central Bangalore (Bengaluru). Patients from across Karnataka and South India visit for FAPI PET CT scans when their oncologist recommends this tracer. Call +91 80505 97975 to check availability and schedule.
Do I need to fast before a FAPI PET CT scan?
No. Unlike FDG PET CT, FAPI PET CT does not require fasting because it does not depend on glucose metabolism. This is a practical advantage for diabetic patients and those who find it difficult to fast.
How is FAPI PET CT different from FDG PET CT?
FDG targets glucose metabolism in cancer cells. FAPI targets fibroblast activation protein in the tissue surrounding the tumour. FAPI has lower background uptake in the brain, liver, and urinary tract, making it better for detecting cancers in these areas. FAPI can also find cancers that are metabolically quiet on FDG.
When should I ask about FAPI PET CT instead of FDG?
Ask about FAPI PET CT if your cancer is in the liver, pancreas, bile duct, or stomach, or if a previous FDG PET CT was inconclusive. FAPI is also useful when your oncologist suspects disease that FDG may not detect clearly.