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Your PSA test result: What’s next?

If the test result hints at cancer, your doctor will need to rule out noncancerous causes and may perform additional tests.

When you take a test for a serious medical condition, most of all you want certainty: Do you have the disease, or do you not? But the only thing that you can rely on about PSA testing for prostate cancer is that the results will be uncertain.

“The problem is that PSA is a nonspecific measurement,” says Dr. Marc B. Garnick, a prostate cancer specialist at Harvard Medical School and Beth Israel Deaconess Medical Center. “It can mean you may have cancer, nothing more.”

Screening means testing a seemingly healthy person for signs of a hidden disease. When used as a screening tool, the PSA test aims to uncover prostate cancer at an early stage, when (hypothetically) it may be more curable. But only one of the two largest and best clinical trials has shown that routine PSA screening decreases a man’s risk of dying of prostate cancer, and then only slightly. Also, screening comes with a risk of a man being diagnosed with and treated for a tumor that might never have become a threat to his health or longevity. (See Harvard Men’s Health Watch, October 2012).

Despite the uncertainties, millions of American men still choose to undergo PSA screening. If you get tested, what can the results tell you? What additional tests and procedures might follow? And what risks do you face? It turns out that, like everything about PSA testing, interpreting the test result is anything but simple. Here is what to expect.

Additional prostate cancer risk tests

  • Free PSA level: PSA circulates in the blood in two forms: bound to other proteins or unbound (free). Some studies suggest that the lower the ratio of free to total PSA, the greater the risk of cancer. The free PSA level may be useful in deciding whether a biopsy is the appropriate next step. But even if the free PSA is favorable, the risk of underlying cancer remains around 8%.

  • PSA density: This number is calculated by dividing the PSA level by the size of the prostate in grams, as measured by ultrasound. The higher the PSA density, the greater the likelihood of cancer. As with free PSA, a PSA density can look normal but you may still have cancer.

  • PSA velocity: Doctors have tried to assess cancer risk based on how rapidly PSA rises over a series of several annual PSA tests, a quantity called PSA velocity. But once again, this strategy has proved unreliable. PSA scores may rise more rapidly in men with cancer—or they may not. “PSA velocity adds very little to the actual PSA value in helping diagnose prostate cancer,” Dr. Garnick says. Still, PSA velocity is something that your doctor may want to know.

  • Prostate health index (PHI): The PHI combines measurements of three forms of PSA that circulate in the blood, including free PSA and a subcategory of free PSA called proPSA (or p2PSA). The PHI is intended to help doctors determine if a biopsy is warranted.

  • PCA3 score: In cancerous prostate cells, the PCA3 gene is highly active. If a doctor massages a cancerous prostate gland, a protein made by the PCA3 gene “leaks” into the urine, where it can be detected with a test. The PCA3 protein level doesn’t rise if a man has a noncancerous prostate condition, so this measurement more closely correlates with cancer than PSA level does. The FDA has not approved PCA3 for routine prostate cancer screening, but some laboratories may offer it.

The test result

Prostate-specific antigen (PSA) is a protein made in the prostate gland. PSA testing measures the total amount of PSA in your blood in nanograms per milliliter (ng/ml). Doctors use the test to screen for prostate cancer because the level of PSA in your blood may rise if you develop a prostate tumor.

Unfortunately, there is no absolute PSA level that always means you have cancer—or that rules out the possibility of cancer. In the past, many doctors have considered a PSA level below 4.0 ng/ml as in the normal range, and a PSA above 4.0 ng/ml as a potential concern. But this rule of thumb is unreliable. In an often-cited study, 17% of men with a PSA of 1.1 to 2.0 had prostate cancer, and 24% with readings of 2.1 to 3.0 had the disease.

To determine if your PSA result requires follow-up, your doctor will take into account a number of factors, including age, race, family history of cancer, the likelihood of other noncancerous medical conditions that affect the prostate gland, and the results of any previous PSA tests.

For example, a man’s average PSA level tends to rise with age, often because his prostate gland grows larger and therefore produces more PSA overall. This means that for a 70-year-old man, a PSA of 5.0 would not necessarily be abnormally high. But a reading of 3.0 in a 50-year-old man could be considered high enough to be a concern.

Deciding to have a biopsy

If your doctor is worried about your PSA result, a next step could be simply to retest. That could help to rule out known reasons for short-term spikes in PSA. Besides prostate enlargement, an infection of the prostate (prostatitis), having ejaculated in the previous 24 hours, or even a long bicycle ride could all cause a temporary blip in PSA.

If you get retested and the result still concerns your doctor, you
may be on your way toward being offered a biopsy. In a prostate biopsy, a device is inserted into the rectum that shoots a needle through the rectal wall into the prostate to remove samples, or “cores,” from multiple locations in the gland. A pathologist examines the samples for cancer.

Biopsy comes with the risk of pain and discomfort as well as infection.
So your doctor may first want to perform additional tests to get a better sense if biopsy is warranted. None of the tests available can confirm the presence of cancer; only a positive biopsy result can do that. But you want to make
sure the biopsy is really necessary
before you go ahead with it. There are additional measurements that your doctor may consider to assess
your risk of cancer (see “Additional prostate cancer risk tests” on page 4).

Uncertain outcome

It’s important to keep in mind that having a PSA test that leads to biopsy, a diagnosis of cancer, and prompt treatment does not guarantee a good outcome. Go into the PSA process with your eyes open and no expectation of easy decisions or simple answers. Do it if your “need to know” whether you have cancer and the possible chance to benefit from early treatment outweigh your concerns about the risks of testing.

Posted by: Dr.Health

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