Ga-68 Fapi PET
Ga-68 FAPI PET/CT images the cancer-associated fibroblasts that surround most carcinomas, showing tumors against a quiet background with no fasting or blood sugar control. It helps where FDG PET struggles, in signet ring stomach cancer, peritoneal spread, pancreatic and bile duct cancer, liver metastases and brain tumors. At Biruni Hospital in Istanbul, our nuclear medicine team reviews your case first, and the scan and report take one to two days.
About This Department
Many cancers build a scaffold of fibroblasts around themselves. Ga-68 FAPI PET makes that scaffold visible.
Ga-68 FAPI PET/CT uses a small molecule, a fibroblast activation protein inhibitor, labeled with gallium-68, to find the cancer-associated fibroblasts that surround and support a tumor. Those fibroblasts appear in the great majority of carcinomas, while healthy organs carry almost none, so tumors stand out against a quiet background. The scan needs no fasting and no blood sugar control. In stomach, duodenal and bowel cancers it detected every primary tumor, against 53 percent for FDG PET, and it found more lymph node, bone and organ spread (Pang and colleagues, Radiology, 2021). It helps most where FDG struggles, in signet ring stomach cancer, peritoneal spread, bile duct and pancreatic cancer, liver metastases and brain tumors. This page explains how the tracer works, how it compares with FDG, the cancers where it changes decisions, false positives, regulatory status, the scan day, radiation dose, FAP-targeted therapy and how patients from abroad arrange a FAPI scan at Biruni Hospital in Istanbul.
What FAPI PET is
Cancer-associated fibroblasts
Normal adult organs express very little FAP, so a tracer that binds it shows tumors with high contrast and little background.
Why fibroblasts matter
The idea turns cancer imaging around.
For two decades PET scanning of cancer has relied almost entirely on FDG, a radioactive sugar taken up by cells that burn glucose fast, and that works well for lymphoma, lung cancer and many others. Yet several cancers burn little glucose, and some organs, the brain and to a lesser degree the liver and bowel, take up so much sugar themselves that tumors disappear against them. FAPI does not look at the cancer cell at all. It looks at the fibroblasts the cancer recruits, which behave in much the same way across tumor types, and so a single tracer shows cancers of the stomach, pancreas, bile ducts, breast, head and neck, and connective tissue with a clarity FDG rarely reaches in those sites.
That breadth explains the attention. Some researchers have called FAPI a candidate for the next pan-cancer tracer.
It will not replace FDG. It fills gaps.
FAPI compared with FDG
| Feature | Ga-68 FAPI | F-18 FDG |
|---|---|---|
| Fasting before the scan | Not needed | Four to six hours |
| Blood sugar control | Not needed | Needed, difficult in diabetes |
| Brain background | Very low | Very high |
| Liver and bowel background | Low | Moderate |
| Signet ring and mucinous tumors | Clear uptake in many | Weak uptake |
| Inflammation and healing tissue | Uptake in fibrosis and scars | Uptake in active inflammation |
FDG measures how hungry the cancer cells are for sugar. FAPI measures the tissue the cancer has built around itself. The two scans answer different questions.
Cancers where it helps
| Cancer | Why FAPI helps | Typical question |
|---|---|---|
| Stomach cancer, including signet ring type | Low FDG uptake in diffuse types | Extent of spread, peritoneum |
| Pancreatic cancer | Dense stroma, high FAP | Staging before surgery |
| Bile duct cancer, cholangiocarcinoma | High uptake, low liver background | Local extent, nodes |
| Colorectal cancer and liver metastases | Low liver background | Number and site of deposits |
| Head and neck cancer | Low uptake in normal mouth and throat | Tumor edge for radiotherapy |
| Sarcoma | Among the highest uptake | Extent, recurrence |
| Breast and lung cancer | High uptake | Selected staging questions |
Where it adds little
Prostate cancer has a better tracer in PSMA, neuroendocrine tumors in DOTATATE, and differentiated thyroid cancer in iodine. Our PSMA PET/CT and PRRT pages describe those scans.
A FAPI scan earns its place when FDG leaves a real question unanswered.
Stomach and bowel cancers
FAPI PET detected more primary tumors, lymph node metastases and bone and organ metastases than FDG PET in 35 patients with stomach, duodenal and colorectal cancer, and changed the stage in a fifth of those not yet treated (Pang and colleagues, 2021).
| Finding | Ga-68 FAPI | F-18 FDG |
|---|---|---|
| Primary tumors detected | 100 percent | 53 percent |
| Lymph node metastases detected | 79 percent | 54 percent |
| Bone and organ metastases detected | 89 percent | 57 percent |
| Uptake in peritoneal deposits, average SUVmax | 8.4 | 3.6 |
Results across cancer types
| Finding | Ga-68 FAPI | F-18 FDG |
|---|---|---|
| Primary tumors detected | 98.2 percent | 82.1 percent |
| Lymph node metastases detected | 86.4 percent | 45.5 percent |
| Bone and organ metastases detected | 83.8 percent | 59.5 percent |
Peritoneal spread
| Method | Strength | Weakness |
|---|---|---|
| CT | Available everywhere | Misses small deposits |
| FDG PET/CT | Whole-body picture | Weak in mucinous and signet ring tumors |
| FAPI PET/CT | High contrast in fibrotic deposits | Uptake also in scars from earlier surgery |
| Diagnostic laparoscopy | Direct view and biopsy | Invasive |
HIPEC candidates
For patients considered for cytoreductive surgery with heated chemotherapy, a FAPI scan helps estimate the peritoneal cancer index before the operation.
Choosing between the scans
We start with the question.
A scan is useful when its answer changes what happens next. In newly diagnosed lung cancer, lymphoma or melanoma, FDG PET/CT remains the standard, and FAPI adds nothing worth the extra cost and travel. For a patient with signet ring stomach cancer whose FDG scan looks clean, for pancreatic cancer before a Whipple operation, for a bile duct cancer whose extent decides between resection and transplant assessment, or for a rising tumor marker after bowel surgery with a negative CT, FAPI may show what the other tests do not. Our nuclear medicine physicians review the pathology and previous imaging first and advise on which tracer fits.
Sometimes neither scan earns its cost.
False positives and limits
| Cause | Where | How we tell it apart |
|---|---|---|
| Scars and healing wounds | Surgical sites, biopsy tracts | Timing, CT appearance |
| Fibrosis and cirrhosis | Lungs, liver, pancreas | Pattern, earlier scans |
| Arthritis and degenerative joints | Spine, shoulders, knees | Location on CT |
| IgG4-related disease and pancreatitis | Pancreas, bile ducts | Blood tests, biopsy |
| Atherosclerotic plaque | Arteries | Linear shape along vessels |
| Normal uterus | Endometrium in women before menopause | Physiological pattern |
FAP appears wherever tissue repairs itself. Any recent surgery, radiotherapy or inflammation can light up and mimic cancer.
- Scars stay FAPI-avid for months, so we record the date of every operation and course of radiotherapy before reading the scan.
- A bright spot needs CT, MRI or biopsy correlation.
- Uptake varies between cancers and between patients, and a negative FAPI scan does not exclude cancer.
Interpretation standards
| Factor | Why | Source |
|---|---|---|
| Treatment history | Scars and radiation fibrosis | Your records |
| CT findings | Shape and density | Same scan |
| Earlier FDG or MRI | Comparison | Imaging you send |
Regulatory status
Is FAPI PET an approved scan?
The scan day
No fasting, no diet and no special preparation. Take your usual medicines and drink water freely.
| Step | Duration | Note |
|---|---|---|
| Registration and cannula | 15 minutes | Bring earlier scans on a disc |
| Tracer injection | A few seconds | Painless |
| Waiting period | 60 minutes | Rest, drink water |
| PET/CT imaging | 20 to 30 minutes | Lie still, breathe normally |
| Report | Next working day | Reviewed with your oncologist |
Radiation and safety
No side effects from the tracer have been reported in the published studies. The amount of molecule injected is tiny.
| Source | Effective dose | Note |
|---|---|---|
| FAPI tracer, 200 MBq | 3 to 4 mSv | Giesel 2019 estimate |
| Low-dose CT for PET | 1 to 4 mSv | Varies with protocol |
| Natural background, one year | 2 to 3 mSv | Varies with place |
| Situation | Advice | Duration |
|---|---|---|
| Driving and work | No restriction | None |
| Close contact with babies | Keep short | Rest of the day |
| Flights | Allowed | Same day |
What the result changes
A scan matters only through the decision it informs.
When FAPI shows the cancer confined to one area, surgery or radiotherapy with curative intent stays on the table, and the radiation oncologist can use the images to draw the target on our Elekta Versa HD linear accelerator more precisely, especially in head and neck and pancreatic cancer. When it shows spread the other tests missed, the plan shifts toward systemic treatment and spares the patient an operation that could not have cured. Both outcomes help.
The report goes to the tumor board. The board decides.
FAP-targeted therapy
For patients from abroad
The length of stay for a FAPI scan is one to two days in Istanbul, the scan on the first and a review of the report with our nuclear medicine physician on the next. You can fly the same day.
One coordinator from the international patients office handles arrangements from the first message through discharge and answers the same WhatsApp number after you return. The office works in English, Arabic, French, Russian, Serbian, Romanian and Spanish and books interpreters for other languages, and it arranges the visa invitation letter, airport transfers, daily transport and accommodation near the hospital. Halal, vegetarian and diabetic meals, a prayer room on site, and a female physician on request wherever the rota allows.
Cost
| Item | Included | Priced separately |
|---|---|---|
| Scan | Ga-68 FAPI tracer, PET/CT imaging | Contrast CT if added |
| Reporting | Written report, physician review | Second tracer scan such as FDG |
| Consultation | Review of prior imaging | Biopsy if needed |
The tracer is produced for each patient, so scans are booked on set days and priced as a single package.
References
- Kratochwil C, Flechsig P, Lindner T, et al. 68Ga-FAPI PET/CT. Tracer uptake in 28 different kinds of cancer. J Nucl Med. 2019;60(6):801-805.
- Giesel FL, Kratochwil C, Lindner T, et al. 68Ga-FAPI PET/CT. Biodistribution and preliminary dosimetry estimate of 2 DOTA-containing FAP-targeting agents in patients with various cancers. J Nucl Med. 2019;60(3):386-392.
- Chen H, Pang Y, Wu J, et al. Comparison of [68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT for the diagnosis of primary and metastatic lesions in patients with various types of cancer. Eur J Nucl Med Mol Imaging. 2020;47(8):1820-1832.
- Pang Y, Zhao L, Luo Z, et al. Comparison of 68Ga-FAPI and 18F-FDG uptake in gastric, duodenal, and colorectal cancers. Radiology. 2021;298(2):393-402.
Editor's note
Written by the Biruni Hospital medical editorial team. Reviewed by Prof. Dr. Burçak YILMAZ, Nuclear Medicine.
Medically reviewed by
Prof. Dr. Burçak YILMAZ
Nuclear Medicine
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