A PSA test is used mainly as a screening test for cancer of the prostate. In men who have been diagnosed with prostate cancer, PSA is measured to determine if the cancer has returned after surgery. It can also be used to determine whether the cancer is growing or shrinking after treatment with hormones or radiation.
The question of whether or not to perform screening tests for prostate cancer remains controversial. PSA testing can be used to detect the earliest stage of prostate cancer, before the disease causes any symptoms. Many experts believe that PSA testing is the best way to reduce a man's chance of dying from prostate cancer. This is because the early stages of prostate cancer are much more likely to be curable.
However, other experts fear that if PSA is overused, some men will be diagnosed and treated for cancers that have little potential to cause harm. Many older men develop prostate cancer that never spreads and never causes any problems. Most of these harmless cancers would go undetected if screening was not done.
In addition, treatment for prostate cancer can have serious side effects. Screening all men for prostate cancer and treating potentially harmless cancer might end up causing more harm than good.
Unfortunately, there is no reliable way to determine in advance which cancers need treatment and which are likely to be harmless.
At present, most expert panels do not recommend routine PSA testing for all older men. Instead, they encourage men who are at risk of the disease to make an individual decision about screening. The decision should be made after discussing the risks and benefits with a health care professional.
A man who decides to undergo screening for prostate cancer might think the following:
"The PSA test is the best way to protect myself from dying of prostate cancer. I know that most men with prostate cancer die from something else. But what if I could have been saved if a diagnosis was made early? For me, I would rather deal with the uncertainty of what an abnormal PSA actually means. Also I am ready to accept the possible side effects of biopsies and treatment. I'm one of those people who just needs to know."
A man who chooses not to be screened might think this way:
"No one is sure if screening really helps, and it may actually lead to unnecessary treatment. I think I'll wait until we have a better test that can predict which men are more likely to die because of prostate cancer."
For men who want to be screened for prostate cancer, the PSA test is usually done every one to two years, beginning at age 50. Men with an increased risk of prostate cancer may wish to begin screening at age 45. African-American men and men whose father or brother has been diagnosed with prostate cancer are at increased risk for prostate cancer. In addition to a blood test for PSA, most doctors also perform a digital rectal exam.
PSA testing is likely to be less useful in men older than age 75 and men who have serious medical problems or other reasons for a limited life expectancy. This is because it may take a decade or more for prostate cancer to grow from the stage at which it can be first detected to the point where it causes symptoms or harm.