prostate cancer screening: should i have a psa test?

prostate cancer is the abnormal growth of cells in the tissues of the prostate gland. most cases of prostate cancer occur after age 65.

early prostate cancer usually doesn't cause symptoms. when prostate cancer is found before it has spread outside the prostate gland, options include active surveillance, surgery to remove the prostate, or radiation. if a prostate cancer grows or spreads, symptoms may develop, including urinary problems (such as blood in the urine) and bone pain.

many prostate cancers grow slowly. this means that many people with prostate cancer will die of something else before their prostate cancer advances enough to cause any problems. with faster-growing prostate cancers, finding the cancer early may not help you live longer. some prostate cancers will be fatal no matter when they're found or how they are treated.

the prostate-specific antigen (psa) test is a blood test that measures your level of psa. the psa test is usually done to screen for prostate cancer in people who have no symptoms.

psa is released into the blood by the cells of the prostate gland. a psa test can show if you have normal or high amounts of psa in your blood. a high psa level can have many causes, including an enlarged prostate, an infection, or, less often, prostate cancer.

psa tests can help find some prostate cancers early. but it may not help you live any longer than if you had no screening.

false-positive results

often the psa test can show high levels of psa that aren't caused by cancer (called a false-positive).

if your psa test is high, you may need more tests—like a prostate biopsy—to check for prostate cancer. these tests can be harmful. for example, prostate biopsies can cause infections. for a few people, these infections are very serious. these tests can also cause a lot of worry.

false-negative results

psa tests may miss some cancers. not all prostate cancers cause a high psa, so some psa tests will be normal when there is cancer (called a false-negative). but the more serious prostate cancers usually do cause a high psa.

overdiagnosis

a psa test can find cancers that would not have caused a problem (called overdiagnosis). you might have this type of cancer, but a psa test can't tell if the cancer is harmless. so you may get cancer treatment—including surgery or radiation—that you don't need.

a psa test alone can't tell if you have prostate cancer. this test only shows the level of your psa. and a psa test can't tell why your level is high. a biopsy is the only way to check for prostate cancer.

the psa test also does not tell you if a cancer is growing fast or slow. most prostate cancers that are found early are slow-growing. but a few prostate cancers grow fast.

these numbers are from a large study done on the value of psa testing. the study was done in europe and did not include people of african descent, who are at higher risk of prostate cancer.^{footnote 3} a smaller study done in the united states did not find that psa testing saved lives.^{footnote 1}

*based on the best available evidence (evidence quality: moderate to high)

benefits

the quality of the evidence about psa benefits is moderate.

a large study of prostate cancer screening showed that out of a group of 1,000 men ages 55 to 69 who have psa testing and are followed over a 13-year period:^{footnote 3}

• prostate cancer is more likely to be found with psa testing than without psa testing. about 102 out of 1,000 men who are screened will be diagnosed with prostate cancer versus about 68 out of 1,000 men who are not screened.
• psa testing may prevent a small number of deaths from prostate cancer. about 5 out of 1,000 men who are screened will die of prostate cancer versus about 6 out of 1,000 men who are not screened.

risks

the quality of the evidence about psa risks is high.

many cancers found by psa tests would not have caused a problem if they had not been found through screening. but when cancers are found, they often get treated with surgery to remove the prostate or with radiation. these cancer treatments may not have been needed. and they can have serious side effects, such as urinary, bowel, and erection problems.

take a group of 1,000 men ages 55 to 69 who have psa tests. about 27 of these men may get cancer treatment they don't need.^{footnote 3}

psa tests can show high levels of psa that aren't caused by cancer (called a false-positive). this means you may need more tests—like a prostate biopsy—to check for prostate cancer. these tests can be harmful. for example, prostate biopsies can cause infections. for a few people, these infections are very serious. these tests can also cause a lot of worry.

out of 1,000 psa tests, about 170 will find a high psa level. but most high psa levels are not caused by cancer. out of those 170 high psa test results, about 129 will not be from cancer, while about 41 of the 170 will be from cancer.^{footnote 3, footnote 4}

understanding the evidence

some evidence is better than other evidence. evidence comes from studies that look at how well treatments and tests work and how safe they are. for many reasons, some studies are more reliable than others. the better the evidence is—the higher its quality—the more we can trust it.

the information shown here is based on the best available evidence.^{footnote 3, footnote 4} the evidence is rated using four quality levels: high, moderate, borderline, and inconclusive.

another thing to understand is that the evidence can't predict what's going to happen in your case. when evidence tells us that 2 out of 100 people who have a certain test or treatment will have a certain result and that 98 out of 100 will not, there's no way to know if you will be one of the 2 or one of the 98.

the canadian urological association (cua) recommends talking to your doctor about the potential benefits and risks of prostate cancer. if you decide that prostate cancer screening is right for you, the cua suggests starting at age 50. if you are at higher risk, the cua suggests starting at age 45.^{footnote 2}

your doctor may recommend psa testing if you have an increased risk of getting prostate cancer. some things that put people at a higher risk include:

• being of african descent.
• having a parent or sibling who had prostate cancer before age 65.
• knowing that a gene change, such as brca, runs in your family.