What Is a PET Scan, and How Is It Used in Prostate Cancer?

When cells in the prostate grow out of control, prostate cancer develops. Prostate cancer is a leading cause of cancer in the United States. Healthcare providers have many tools to evaluate prostate cancer. One tool is the PET scan. If you need a PET scan, here’s everything you need to know about how PET scans work and what you need to do to prepare for yours. 

What is a PET scan?

A positron emission tomography study, or PET scan, is a type of imaging study. During a PET scan, you take a small amount of radioactive material, called a “tracer.” The tracer is very safe because only a tiny amount is used. 

There are many types of tracers, but there are two new tracers that are more common than the rest. These tracers stick to a protein that’s only found on prostate cancer cells. Once it’s stuck to the prostate cancer cells, it gives off energy. Cameras can capture this energy, which healthcare providers can then see on images. When you get a PET scan, you can actually see where the cancer cells are in your body. 

When do you need a PET scan for prostate cancer?

You may need a PET scan during your prostate cancer treatment for several reasons, including:

• Staging: Not all prostate cancers are the same. Based on your biopsy and other test results, your prostate cancer may be more likely to move outside of the prostate. If this is the case, a PET scan can tell how far the cancer may have advanced. Staging shows how much cancer is in the body, which can affect treatment decisions.

• Metastasis: PET scans can look for new metastases, or areas where the cancer has spread. Newer PET scans, called “PSMA-PET scans” are more accurate for detecting metastatic prostate cancer. They can find evidence of metastases earlier, which means you can get treatment sooner.

• Response to treatment: Once you start treatment for prostate cancer, you may need a PET scan, a prostate-specific antigen (PSA) test, and others to make sure your cancer is responding to treatment.

• Monitoring for recurrence: After you finish treatment, you’ll have regular follow-ups to look for any signs of recurrence. If there’s concern that your prostate cancer has returned, you may need a PET scan to look for new cancer cells. 

What should you expect during a PET scan?

There’s not much you need to do to prepare for your PET scan. Depending on the type of tracer you’re getting, you might need to:

• Avoid eating or drinking anything for 6 hours before your scan. But you can drink water and take routine medication.

• Eat high-protein, low-carbohydrate foods for your last meal before the scan. 

• Avoid exercise for 24 hours before the scan.

The newer tracers that are specific for prostate cancer don’t require any of these restrictions. So if you are having a PSMA-PET scan, you won’t need to stop eating, drinking, or exercising. Your healthcare team will confirm what restrictions you may need.

The day of your PET scan, here’s what to expect:

• You’ll check in and be asked some basic questions. Let the team know about any medications you take and if you have any allergies. 

• A healthcare provider will insert an intravenous (IV) line, usually in your arm. 

• You’ll be given the tracer through the IV. You might feel some coolness as the tracer moves into your arm — this is normal. Allergic reactions to the tracer are very uncommon.

• It takes about 60 minutes for the tracer to stick to the cancer cells. Depending on the type of tracer you get, you’ll be asked to lie down during this time and not walk around. Moving around can affect how the tracer gets distributed in your body.  

• After the waiting period, you’ll get your pictures taken. You’ll be asked to lie on the imaging table and remain still for about 20 to 40 minutes. 

• You won’t feel any pain while you're having the pictures taken, but if you have pain when lying on your back, let your healthcare team know. They can prescribe medication to keep you comfortable during the scan.

• During the PET scan, you’ll be in an enclosed space. If enclosed or tight spaces make you anxious, let your healthcare team know before your exam. They can order medication to make you more comfortable.

After the scan is over, you’ll have a small amount of tracer left in your body. You can drink a normal amount of fluid to flush the tracer out of your body. It will come out in your urine and stool over the next 24 hours. The amount of tracer you got was very small — you won’t need to stay away from friends or loved ones after the scan. 

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Written by:

Brian Clista, MD

Dr. Clista is a board-certified pediatrician who works in private practice in Pittsburgh, Pennsylvania. He previously served as a National Health Service Corporation Scholar in the inner city of Pittsburgh for 11 years.

Edited by:

Patricia Pinto-Garcia, MD, MPH

Patricia Pinto-Garcia, MD, MPH, is a medical editor at GoodRx. She is a licensed, board-certified pediatrician with more than a decade of experience in academic medicine.

Reviewed by:

Brandon R. Mancini, MD, MBA, FACRO

Brandon R. Mancini, MD, MBA, FACRO, serves as medical director at BAMF Health in Grand Rapids, Michigan in the emerging field of theranostics. His primary clinical focus is on the treatment of people with metastatic prostate and neuroendocrine cancers.

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