Prostate-specific antigen (PSA) is a protein produced by the prostate and found in the blood.
A PSA blood test can detect prostate cancer early, but it may not save lives. Sound confusing? It is. Many prostate cancers grow slowly, so a PSA test may save the lives of some men while causing others to have unnecessary surgeries or radiation treatments, which could cause lifelong problems such as erectile dysfunction or incontinence.
Here's what you need to know about PSA tests before having one.
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Low PSA is good
Low PSAusually about 4 nanograms per milliliter of blood or lesssuggests that a man does not have prostate cancer. But higher levelstaking into account age and race (PSA rises naturally with age)may indicate the presence of cancer.
But so many factors influence PSA that a single test is never enough to diagnose prostate cancer. If you do have high levels of PSA, your doctor may suggest a prostate biopsy or another test to determine if you have cancer.
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False positives are possible
Swelling of the prostate gland, infection, and recent ejaculation, among other things, can elevate PSA levels. These factors, however, have nothing to do with prostate cancer. Benign prostatic hyperplasia, or enlarged prostate, which is one of the most common conditions that affect men as they age, also can raise PSA.
If your PSA is elevated, your doctor may first address other issues, such as treating an infection, and then test you again to see if the levels go down.
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Other risk factors are important
If your PSA is high, your doctor will look at other risk factors to decide if you need additional testing. These risk factors include race (black men are more prone to prostate cancer than white or Hispanic men), age (prostate-cancer risk increases with age), and family medical history (men who have an immediate family member with prostate cancer are at increased risk).
If, however, your prostate-cancer risk is lowif, for example, you have no risk factors and a digital rectal exam reveals no abnormal-feeling areas in your prostateyour doctor may decide to forego a biopsy and instead do another PSA test a few months or so down the road.
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Most biopsies don't show cancer
If you need a biopsy, this office-based procedure is used to collect samples of your prostate tissue via a hollow needle. (An ultrasound probe in the anus is used to guide the procedure.)
Approximately three out of four men who have biopsies after positive PSA tests are cancer-free, according to one large study.
"The downside of getting a biopsy is there's about a 3% chance of having a bad infection from it, and it's anxiety producing," says Tracey Krupski, MD, a urologic oncologist and assistant professor of urology at the University of Virginia, in Charlottesville.
That may be too late, says James Mohler, MD, a professor of oncology at the Roswell Park Cancer Institute, in Buffalo, N.Y.
"We'd love to have a better test than PSA," says Dr. Krupski. "We're working on it."
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Testing has a psychological impact
Even if your biopsy results show you're cancer-free, you may experience some psychological aftereffects. One study that tracked men for up to three months after they received a negative biopsy found that the men were still anxious about cancer, and many had symptoms of depression.
"There's definitely a negative psychological effect," says Richard Hoffman, MD, a professor of medicine at the University of New Mexico School of Medicine, in Albuquerque.
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PSA tests may not save lives
The life-saving benefit of PSA tests may be smallif there is one at all. In 2009, a large study in Europe found men ages 50 to 74 who got PSA tests every four years were 20% less likely to die of prostate cancer than men who weren't screened.
One life would be saved for every 1,400 men tested over a nine-year period, according to the study. Another recent study of men in the United States, however, found annual PSA tests didn't decrease the risk of dying from prostate cancer.
But the tests may nevertheless be worthwhile. "Since we've been doing PSA testing in America, we've had the largest drop in mortality from prostate cancer of any country," Dr. Krupski says.
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Healthy men over 75 can skip the test
At age 65, you may want to consider having regular PSA tests for a few more yearsif you're in good health, says Dr. Mohler, who is chairman of the NCCN Guidelines Panel for Prostate Cancer.
"Everyone who gets to age 75 with a normal exam and a normal PSA absolutely should stop," he adds. Older men are likely to outlive any prostate cancer identified after that point, Dr. Mohler says. The ACS guidelines recommend PSA testing only in men who expect to live at least another 10 years.
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Rate of rising PSA is important
Doctors may use the rate at which a man's PSA levels change over time to determine if he should undergo further testing.
For example, men who are undergoing "watchful waiting"the monitoring of low-risk prostate tumors before resorting to treatmentmay be candidates for treatment if their PSA rises more than 0.75 ng/mL each year.
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There's decision-making help
It's no secret that doctors are pressed for time. During a regular office visit they may only be able to give you the most basic information on the PSA test.
But it's a complicated issue. For more guidance, you can check out the American Cancer Society's list of free decision aids on prostate-cancer screening. These are step-by-step guides to help you figure out whetherand howyou should get tested and treated for prostate cancer based on your own values and concerns.
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Test or not? It's your decision
The decision to get screened is yours, says Dr. Hoffman.
If you're not anxious about prostate cancer but you are concerned about the side effects of testing and treatment, for example, it may make sense for you to skip screening. On the other hand, if you know all these side effects and are concerned about prostate-cancer risk, you should get screened.
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You can avoid unnecessary treatment
Doctors are getting better at spotting low-risk prostate cancers, Dr. Krupski says. You can opt for "watchful waiting" (also called "active surveillance"), which is close monitoring of tumors rather than immediate treatment. Still, it's a judgment call.
"This simple blood test enters them into this cascade of downstream events that leads to a lot of uncertainties and trade-offs between benefits and harms," Dr. Hoffman says. "Not just the biopsy, but also the diagnosis and treatment, because if you don't consider that you could be unpleasantly surprised down the road."
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