FAQ: prostate-specific antigen (PSA) test

There is no doubt that the prostate-specific antigen (PSA) test can detect prostate cancer in men who otherwise appear healthy. But critics say the test produces too many false alarms and often leads to needless surgery, radiation and other medical procedures. These guidelines will tell you more.

Deciding to have a blood test that detects cancer when it's still treatable sounds like the ultimate no-brainer. Yet the prostate-specific antigen (PSA) test, which can identify men who have early-stage prostate cancer, has been controversial since its introduction in the late 1980s. It's tough to find a definitive answer.

Most medical groups recommend only that men discuss the PSA test with their doctors. Many doctors are firm believers in the PSA test, pointing to a decrease in deaths from prostate cancer since the test was introduced (though it's not clear what actually caused the drop). The American Urological Association encourages men to begin having annual PSA tests when they turn 50, or 40 if they have a high risk of prostate cancer because of their race (African-American males are at increased risk) or a family history of the disease.

Meanwhile, other physicians point out that up to 30 percent of tumours detected by PSA tests and other forms of prostate cancer screening grow very slowly, won't spread and would never kill a man. Unfortunately, there is no reliable way of telling whether a tumour will remain dormant, so most men diagnosed with early-stage prostate cancer undergo some form of treatment, such as surgery to remove the gland or radiation therapy to destroy cancer cells. These treatments are usually successful but can cause erectile dysfunction, diarrhea and incontinence.

Maybe. By tracking how fast PSA rises and testing "free PSA," doctors may be better able to predict which men are truly at risk.Many doctors today carefully track PSA velocity — that is, how much a man's PSA rises over time. PSA naturally goes up as a man ages, but a rapid increase may be cause for concern. Your doctor may mention one of several variations on the PSA test that have been introduced in recent years and are designed to make it more sensitive.

One of the more widely used new exams compares a man's level of PSA that's bound to other proteins in the blood with his unbound, or "free," PSA. Men with high levels of free PSA (more than 25 percent) have a low risk of prostate cancer. One study suggests that measuring free PSA in men with borderline-high total PSA could eliminate up to 20 percent of unnecessary biopsies.

You do. It's far from perfect (and even less popular), but the exam may improve cancer detection. Doctors perform the test by inserting a gloved finger into a man's rectum and feeling the prostate for abnormal growths. It's not as accurate as a PSA test. For starters, a physician can touch only the back and sides of the prostate. In addition, doctors don't agree on what an abnormal prostate feels like. One review found that the test detects fewer than 60 percent of prostate tumours. But having a PSA test and a digital rectal exam may turn up more cases of prostate cancer.

A study of 6,630 men found that having both exams detected 26 percent more tumours than the PSA test alone.

One caveat:  having both tests also increases the risk of a false-positive test result.