Prostate cancer that spreads or comes back after treatment is often small and hard to detect. A new test called a PSMA PET scan makes these tumors easier to spot. It can also pick up advanced cancers that standard tests like computerized tomography (CT) and bone scans often miss.
How a PSMA PET Scan Works
A positron emission tomography (PET) scan tracks a small amount of a radioactive compound or tracer as it moves through your body.
Most PET scans use a type of sugar as a tracer. PSMA PET scans use a new tracer called gallium 68 PSMA-11.
It targets a protein called prostate-specific membrane antigen (PSMA). You can find it on all prostate gland cells, but cancer cells have far more PSMA than normal. The tracer binds to it and lights up on the scan, even in tiny amounts. This helps your doctor pinpoint whether and where your cancer has spread.
Who Might Need a PSMA PET Scan
Your doctor may recommend it if you:
- Are more likely to have prostate cancer that spreads. This may depend on your biopsy results and some other things.
- Have a high PSA after prostate cancer surgery or radiation therapy. A high PSA may be a sign of cancer, but it can also be a sign of some things that aren’t cancer.
- Have a few small metastasized tumors (your doctor will call them oligometastases) when you’re diagnosed.
How a PSMA PET Scan Works
The first step is to inject the tracer.
A technician will do this through a vein in your arm or hand. You might feel a slight sting from the IV. You need to wait an hour for your body to absorb the tracer.
When you’re ready, you slide into the PET scanner. The scan itself takes about 30 minutes. After the test, you can go about your day as usual.
The tracer can cause nausea, diarrhea, or dizziness. Your doctor may tell you to drink lots of water to help flush it from your system.
Why You Might Want a PSMA PET Scan
There are several advantages to getting a PSMA PET scan, including:
It can find very small tumors much better than standard tests. In one study, PSMA PET scans found 85% of metastatic tumors, compared to only 38% with CT and bone scans.
It’s specifically linked to PSMA. So there’s less chance the test will mistake other problems for cancer.
It’s much less likely to make equivocal findings. This means your results will likely be more definite, one way or the other.
It guides your treatment and helps you avoid tests and treatments you don’t need. For example, if your cancer has spread beyond your prostate gland, surgery to remove it won’t help.
You get less radiation than with other scans.
Concerns About PSMA PET Scans
There are also some things that you might want to keep in mind as you consider whether or not to get a PSMA PET scan. For example:
They cost much more than CT and bone scans. Doctors hope that as more people get the scans, the price will come down.
There is some radiation. Depending on how much radiation you've had before, this might raise your chance of more cancer.
Be sure to talk with your doctor about whether a PSMA PET scan is a good idea for you.