Examples of outcomes with and without PSA testing*
|Outcomes||With PSA testing||Without PSA testing|
|Death from prostate cancer within next 10 years, men ages 45 to 80 ||7 to 8 out of 100||7 to 8 out of 100|
|Cases of cancer found ||6 to 7 out of 100||4 to 5 out of 100 |
|Results above normal range that are not cancer ||76 to 83 out of 100 abnormal results||None|
|Problems from biopsy done after positive test||Less than 1 out of 100 ||None|
*Based on the best available evidence (evidence quality: borderline to moderate)
The quality of the evidence about PSA benefits is borderline.
It's easy to assume that cancer screening tests save lives. And some do. But in the case of prostate cancer screening, PSA testing has not been shown to reduce a man's risk of dying in the next 10 years.
Take a group of 100 men, ages 45 to 80 . Whether they have PSA tests or not, 7 to 8 out of 100 may die of prostate cancer in the next 10 years, which means that 92 to 93 out of 100 may not. Their risk of death from prostate cancer is the same with or without PSA tests.
One benefit may be that cancer is more likely to be found with PSA testing than without. Take a group of 100 men :
- If all of them have PSA tests, testing may find 6 to 7 cancers.
- If none of them have PSA tests, 4 to 5 cancers may be found.
But this can be a mixed blessing. Some prostate cancers that are found may never have caused a problem or needed treatment had they not been found.
The quality of the evidence about PSA risks is moderate.
One risk of PSA tests is that they can suggest a problem when there isn't one. This is called a false-positive result.
It can lead to more invasive testing.
Take a group of 100 men who have a positive PSA test . Only 17 to 24 of these men actually have prostate cancer. This means that 76 to 83 of them do not have prostate cancer, even though their PSA results are positive.
If your PSA test is positive, your doctor may recommend a biopsy, which is the only way to make sure you have prostate cancer.
Biopsy has its own risks. Take a group of 100 men who have a prostate biopsy . Less than 1 out of 100 will have a problem from the procedure, such as infection, bleeding, a blood clot, or problems urinating. (Out of 1,000 men who have a biopsy, 1 to 7 will have a problem from the procedure. This means that 993 to 999 out of 1,000 will not have any problem.)
Another risk is over-treatment. Over-treatment means that a cancer that would never cause a problem for a person is treated as if it were life-threatening, with surgery, radiation, or another treatment, such as chemotherapy. Take a group of 100 men who have prostate cancer found by a PSA test. Some experts believe that as many as 50 out of 100 will have treatment they never needed.1
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.2, 3, 4, 5, 6, 7, 8 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 may have a certain result and that 98 out of 100 may not, there's no way to know if you will be one of the 2 or one of the 98.