A prostate-specific antigen (PSA) test is a blood test that measures the level of a protein called prostate-specific antigen (PSA), which is made by cells in the prostate. Doctors use the test to detect prostate cancer, but it does not provide a definitive diagnosis.
The downside to testing is that an elevated PSA cannot differentiate aggressive tumors from slow-growing, harmless ones that might never cause symptoms during a man's life. Nor can it differentiate cancer from BPH or prostatitis. As a result, it can cause needless worry -- and may lead to costly and invasive procedures, such as biopsies, to determine if cancer is present. Conversely, PSA screening doesn't detect all cancers, so a normal PSA level may offer a false sense of security. Many men with cancer confined to the prostate have normal PSA values. Even advocates of PSA testing doubt its value in men with less than a 10-year life expectancy (ages 75 or older, for men in average health) because these men are more likely to die of something else first.
Studies question the benefit of PSA screening -- does it save lives by enabling doctors to treat aggressive prostate cancers early, or does it harm men who would never die from the disease by subjecting them to the side effects of treatment?
Even though PSA screening increased the diagnosis of prostate cancer, it did not improve the prostate cancer survival rate, and showed no real differences in the numbers of deaths from other causes.
In the United States, the lifetime risk of dying from prostate cancer is 3%. A 27% relative risk reduction would mean that, with screening, the risk of dying from prostate cancer would drop from 3% to 2.19%.
In Europe, that modest benefit came at a steep price. Researchers calculated that 48 men who are not at risk of dying from prostate cancer would have to be treated in order for screening to prevent one death from the disease over nine years. In other words, 48 men would risk the side effects of treatment to save one life.
One conclusion that can be drawn from the studies: men should think carefully about PSA screening and discuss the risks and potential benefits with their doctors before having the test.
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