The ProstaScint scan, also known as the prostate-specific membrane antigen (PSMA) study, is used to help your doctor identify the spread of prostate cancer. It’s only used in people who have already been diagnosed with cancer. It can help determine if you have advanced cancer or a cancer that has metastasized or spread to soft tissue beyond your prostate.
Keep reading to learn more about this procedure.
Who’s a good candidate for a ProstaScint scan?
The ProstaScint isn’t usually used to screen for prostate cancer or to see how well a certain treatment has worked. Instead, your doctor may use the scan after you’ve been diagnosed to determine how advanced your cancer is and how much it has spread to soft tissues outside the prostate.
ProstaScint scans may be more accurate in people with a higher risk for metastatic cancer. The scan is not recommended in people who are at a low risk for metastasis because of the potential for false positive test results. Your doctor will usually estimate your risk of metastasis using a number of factors and, based on your risk level, determine if a ProstaScint scan is recommended.
While a ProstaScint scan is not recommended to measure the effectiveness of a treatment, there are circumstances in which it will be used after treatment has begun. Your doctor may recommend a ProstaScint scan if you’ve had a prostatectomy and they think you may have a recurrence of cancer outside of the prostate. A prostatectomy is surgery to remove all or part of the prostate gland. There’s evidence from an older study from 1998 that the scan could also help detect recurrence after hormonal or radiation therapy, but this approach is not standard practice, and newer research is needed.
Preparing for the procedure
A ProstaScint scan will usually take two to three visits. The scan is done at a nuclear imaging center. The first visit usually doesn’t require any specific preparations. The day before your final scan, however, your doctor might ask that you follow a clear liquid diet and drink magnesium citrate, a laxative.
Insurance coverage of the ProstaScint scan varies, but the majority of insurance companies and Medicare cover the procedure. It’s always a good idea to call your insurance provider beforehand to confirm coverage.
During the procedure
During your first appointment, a technician will inject a mixture into your bloodstream and you’ll have a short imaging scan. The mixture contains a protein that has a radioactive molecule — the isotope Indium-111 — linked to it. The protein specifically attaches to prostate cancer cells so that a radiological camera can detect only those cells.
After your first visit, you’ll wait three to six days before your final scan. That will allow the isotope to clear from the rest of your body. Each scan will last between one and three hours.
The scans use a single-photon emission computed tomography (SPECT) machine to detect the radioactive isotope attached to cancer cells. This machine circles a “gamma camera” around you to detect radioactivity while you’re lying still. Sometimes, a ProstaScint scan is done together with a technetium-99m-labeled red blood cell scan. That scan helps to visualize blood vessels around the prostate gland by a similar method of detecting radioactivity. In addition, the SPECT scan is sometimes combined with a type of X-ray scan called a computerized tomography scan (SPECT-CT). This is more expensive, but more precise. After your scans are finished, a radiologist will interpret the images and send the results and findings to your doctor.
The ProstaScint scan usually does not cause adverse reactions and meets radiation safety standards. It was approved by the U.S. Food and Drug Administration in 1996. The amount of radiation you would receive from this scan is small and about the same amount you’d receive from an X-ray procedure.
Understanding your results
Your doctor can use your ProstaScint results to help determine the stage of your cancer. That can help your doctor recommend an appropriate treatment plan.
The ProstaScint scan is much more accurate than CT scans or MRIs for evaluating prostate cancer metastases. Doctors and scientists have also improved its accuracy since it was first used in the 1990s. This is because doctors now better understand what the results mean, and the scan can be combined with other imaging techniques to make it more precise.
However, the ProstaScint scan has limitations and can be inaccurate. This means that your doctor will not use the ProstaScint scan alone to understand your cancer. For example, a ProstaScint scan will only detect prostate cancer cells in soft tissue. Your doctor will likely order a bone scan to detect any metastases into your bones.
The ProstaScint scan is a radiological imaging tool that can help your doctor identify the spread of prostate cancers in some people. It’s a relatively new test, and more research is needed to better understand the use of this test.
The procedure may be beneficial for men who:
- are newly diagnosed with high-risk prostate cancer
- have had a prostatectomy and may have a recurrence of cancer
Your results can help inform your treatment plan, though other factors such as your PSA levels, Gleason score, and digital rectal exam results will also be considered. If your cancer has not metastasized, surgery and radiation may be recommended as treatment options. If your cancer has spread and is more advanced, your doctor may recommend hormone therapy.