• Conventional tests for metastatic prostate cancer have limited accuracy, which contributes to under-diagnosis and under-treatment of metastatic disease.
  • The prostate-specific membrane antigen (PSMA) PET scan is a new test that appears to be more accurate than conventional alternatives for detecting metastatic prostate cancer.
  • New treatments under study seek to target PSMA, which in combination with more accurate testing could improve outcomes for people with metastatic prostate cancer.

Prostate cancer is one of the main causes of cancer-related death among American men, reports the American Cancer Society. Accurate diagnosis and treatment are important for improving survival in people with this disease.

Metastatic prostate cancer is prostate cancer that has spread beyond the prostate gland to other parts of your body. Although prostate cancer is easier to treat before it spreads, treatments for metastatic disease can improve survival and quality of life.

Conventional tests for metastatic prostate cancer have limited accuracy. This contributes to under-diagnosis and under-treatment.

A new test known as the PSMA PET scan appears to be more accurate and may improve diagnosis of metastatic disease. Although more research is needed, it may be especially helpful in combination with new treatments currently being studied for metastatic prostate cancer.

“With [recent] FDA approval, this test will be a game changer for men with high-risk disease,” Dr. Louis Potters told Healthline. Potters is the deputy physician-in-chief of Northwell Health Cancer Institute in Lake Success, New York.

“This test… may have a huge impact on the type of therapy that would be most effective [for them].”

Read on to learn how the PSMA PET scan may improve metastatic prostate cancer diagnosis and treatment.

If your doctor suspects that you might have prostate cancer, they may order one or more of the following tests:

  • Digital rectal exam (DRE). Your doctor inserts a lubricated finger into your rectum to feel for hard areas or bumps on your prostate gland that might be cancer.
  • Prostate-specific antigen (PSA) blood test. A healthcare professional draws a sample of blood to measure your level of PSA, a protein produced in your prostate gland. High PSA levels may be sign of prostate cancer.
  • Prostate biopsy. A urologist uses a small needle to collect tissue samples from your prostate. These samples are examined under a microscope for cancer cells.
  • Imaging test. An MRI (magnetic resonance imaging) or transrectal ultrasound (TRUS) may be performed before, during, or after a biopsy to help locate abnormal tissue in the prostate.

The results of these tests can help your doctor not only diagnose prostate cancer but also assess your risk of metastatic disease.

If your doctor suspects that you have metastatic prostate cancer, they’ll order imaging tests to check for tumors in your lymph nodes, other organs, and bones. Metastatic tumors are also known as metastases.

Doctors have conventionally ordered a combination of imaging tests to check for metastatic prostate cancer. These tests typically include:

  • a CT or MRI scan, to check for metastases in your lymph nodes and other organs
  • a bone scan, to check for metastases in your bones

Although these tests provide more information than a PSA blood test and biopsy alone, they have limited accuracy. As a result, some people with metastatic prostate cancer may experience delays in diagnosis and treatment.

One 2020 study found that the combination of CT and bone scans was only 65 percent accurate at detecting metastases in men with prostate cancer. The same study found that the PSMA PET was 92 percent accurate at detecting metastases.

In other words, the PSMA PET was 27 percent more accurate than the more conventional testing approach.

“Phase III, randomized studies have shown that PSMA PET-CT is superior to conventional radiology studies such as nuclear medicine bone scan, CT, or MRI, in detecting metastatic disease,” Dr. Michael Feuerstein, urologist at Lenox Hill Hospital in New York City, told Healthline.

“This is important in determining your prognosis and the appropriate treatment recommendations.”

The PSMA PET scan is an imaging test that uses a special dye with radioactive tracers to make prostate cancer cells show up more clearly.

In late 2020 and in 2021, the Food and Drug Administration (FDA) approved two tracers for this test:

  • Gallium 68 PSMA-11 (GA-68 PSMA-11)
  • Pylarify (piflufolastat F 18, 18FDCFPyL)

These tracers bind to prostate-specific membrane antigen (PSMA), a protein that’s found in high levels on prostate cancer cells. This makes prostate cancer cells appear more clearly on a PET-CT or PET-MRI scan.

Your doctor may order a PSMA PET scan if you’ve recently been diagnosed with prostate cancer and they suspect the cancer may have already spread.

According to guidelines from the Society of Nuclear Medicine & Molecular Imaging, PSMA PET is appropriate for people with newly diagnosed prostate cancer that is classified as one of the following:

  • unfavorable intermediate risk
  • high risk
  • very high risk

Your doctor will assess your risk group based on your PSA level, biopsy results, digital exam, and any imaging tests results that you might have already received.

Your doctor may also order a PSMA PET scan if you’ve already undergone surgery or radiation to treat prostate cancer, but the cancer remains detectable or appears to have returned. Cancer that returns following successful treatment is known as recurrent cancer.

“Patients should ask their doctor if they are suitable candidates for PSMA PET-CT at the time of prostate cancer diagnosis or suspected prostate cancer recurrence,” said Feuerstein. “The cost may vary by hospital or geographic region. However, the cost should be weighed against the benefit of more accurate cancer staging and treatment recommendations.”

The recommended treatment plan for prostate cancer varies depending on several factors, including whether the cancer has spread or recurred. Accurate staging is essential for determining the best treatment approach.

“Improved staging at the time of prostate cancer diagnosis or suspected prostate cancer recurrence will ensure that you receive the proper treatment and are not under- or over-treated,” Feuerstein explained.

If you have prostate cancer that hasn’t yet spread, your doctor may recommend surgery to remove your prostate gland, radiation therapy to kill cancer cells, or a combination of both. If the cancer is slow growing, your doctor may counsel you on the options, such as waiting to start treatment.

If you have metastatic prostate cancer, your doctor will likely prescribe radiation or hormone therapy (androgen suppression therapy) or both rather than surgery. Hormone therapy lowers levels of the hormone androgen, which slows the growth of prostate cancer.

Your doctor may also prescribe chemotherapy, medications, or other treatments to manage more advanced cancer.

PSMA PET scans may help people with metastatic prostate cancer get earlier and more accurate diagnoses. This may help them avoid unnecessary surgery and begin hormone therapy earlier. Although more research is needed, this might help improve their survival, quality of life, or both.

Researchers have also been developing new treatments that target PSMA. This is the same protein detected by the PSMA PET scan that is elevated in people with prostate cancer.

“An exciting new development is PSMA-directed therapies for treating men with metastatic disease that no longer responds to androgen-deprivation therapy or chemotherapy,” said Feuerstein.

“A recent phase III, randomized trial demonstrated improved overall survival in men treated with lutetium-labeled PSMA-617, a [radioactive substance] that seeks out PSMA-expressing prostate cancer cells and delivers radiation that destroys the cancer cells,” he explained.

Other recent research has also found that lutetium-labeled PSMA-617 improved progression-free survival and overall survival compared to current standard treatments for metastatic prostate cancer in men whose cancer is resistant to hormone therapy.

The PSMA PET scan is a new test for metastatic prostate cancer. It locates the protein PSMA throughout the body, which is found in high levels on prostate cancer cells.

Compared with more conventional tests, it appears to be more accurate at diagnosing prostate cancer that has spread to the lymph nodes, other organs, or bones.

New treatments also seek to target PSMA-expressing prostate cancer cells. The combination of improved diagnosis and new medications may lead to improved treatment of the disease and improved outcomes.