Research has not yet clearly shown if the benefits of testing for prostate cancer outweigh the harms. Because of this, different health and advocacy groups have conflicting messages and there are different practices among doctors. If you’re a man with an average risk of developing prostate cancer, this can be especially confusing.
Early testing can help detect prostate cancer
The PSA (prostate specific antigen) test was first developed to monitor the progression of prostate cancer and to watch the tumour’s response to treatment.
When combined with a digital rectal exam (DRE), the PSA test can also be an effective test to help find (diagnose) cancer in men who have symptoms of prostate cancer. If prostate cancer is suspected, further tests (TRUS and biopsy) are needed to confirm the diagnosis.
Limits of prostate cancer testing
The PSA and DRE tests have a high rate of false-positive results. A false positive means that the test result suggests cancer, even though there is no cancer. In other words, it’s like a false alarm. A false positive result can lead to unnecessary and invasive follow-up testing. Research shows that up to 20% of men may experience side effects such as blood in the urine, pain and temporary impotence from a trans-rectal needle biopsy.
PSA and DRE tests can also give false-negative results. This means no cancer is detected, even though cancer is present. Getting a false-negative result can cause you or your doctor to ignore symptoms of prostate cancer. The U.S. Preventive Services Task Force estimated in 2002 that 10%–20% of early prostate cancers are missed by PSA testing.
The PSA test may detect prostate cancer that will not grow or spread during a man's lifetime. In these cases, doctors may suggest active surveillance (often called watchful waiting) of the prostate cancer. For active surveillance, the doctor monitors the cancer regularly rather than immediately starting treatment with surgery, radiation or medication.
Deciding what to do in this situation can be a difficult decision. It is useful to know that unlike many other cancers, some men have prostate cancer for years without it affecting their health. Recent research has shown that up to 50% of cancers that are detected by the PSA test may never need to be treated. Detection of these types of prostate cancer tumours is called over-diagnosis. An over-diagnosis can increase stress and anxiety. Some men may also have unnecessary treatments that expose them to more serious risks. For example, a radical prostatectomy (removal of the entire prostate) and external beam radiation can cause sexual dysfunction and/or urinary problems. Hormone drug treatment can lead to sexual dysfunction, breast swelling and hot flashes.
Can prostate cancer testing save lives?
For men who do not have symptoms of prostate cancer, the research findings are not clear. No screening test is 100% accurate. A good screening test results in decreased death rates in people with cancer. However, researchers also look for other benefits of screening including improved quality of life and less harmful treatments.
Although death rates from prostate cancer have decreased over the years, research suggests that this is likely due to changes in how prostate cancer is diagnosed and treated. More research is needed to determine if PSA testing saves lives or not. Two major studies that are continuing to study PSA testing alone or in combination with DRE are:
Both of these studies published initial results in 2009 and are continuing to study the men. The initial results from these trials further support the need for men at average risk to talk to their doctor about the risks and benefits of having PSA screening to decide what is right for them.
The PLCO trial includes over 75,000 men. Half the men have regular DREs, PSA tests or both. The other half is the control group and do not receive the tests. The purpose of the study is to see if testing for prostate cancer will save lives. The initial results published in March 2009 showed that PSA testing does not reduce the number of prostate cancer deaths. These are early results and further study is needed.
The ERSPC study includes over 250,000 men in 8 European countries. Half the men had an initial DRE and PSA test. Some men also had a TRUS (transrectal ultrasound). The other half of the men is the control group and will receive no testing. Initial results from 162,000 men in 7 of the study centres were published in March 2009 and showed that PSA testing can reduce cancer deaths by 20%. However, it also showed that the men getting PSA testing have a high rate of over-diagnosis. They found that 50% of prostate cancers detected by PSA would not have become a health issue and may not have needed treatment.
Researchers are also studying new ways to use PSA testing, including:
- Serial PSA testing, including PSA velocity and PSA doubling time: Serial testing checks the PSA levels repeatedly over time and compares the findings with earlier results. Some research suggests that if a PSA level increases quickly, it may indicate cancer. Serial PSA testing is already an important tool for monitoring prostate cancer while in treatment.
- PSA density: This monitors the level of PSA compared to size of the prostate. Some older men develop enlarged prostates that are not cancerous. In this test, comparing the PSA level to the size of the prostate gives a more accurate normal range for PSA levels.
- PSA ratio: PSA can exist in 2 forms in the blood. This test checks the amount of one form compared to the other form. Some research shows that an abnormal ratio can indicate cancer.