In a Swedish study, men who underwent PSA testing had 44% fewer deaths from prostate cancer in the next 14 years than men who did not undergo the testing. The benefit was even larger in men who were under 60 at the start of the study.

Over 14 years of follow-up, there were 78 deaths from prostate cancer in the unscreened group and 44 deaths from prostate cancer in the screened group.

PSA testing has become controversial. While it helps detect prostate cancer early, many of the cancers it detects are so small that they will never affect the patient. This can lead to unnecessary treatments that leave patients no better off than they started and may even worsen their quality of life. There is also debate over whether PSA testing ultimately saves lives, and if so, how many.

This study indicates that PSA testing does in fact save a substantial number of lives.

The still-ongoing study was of 20,000 men, aged 50-65. The men were randomly assigned to either have PSA screening once every two years or not to have their PSA tested. Men whose PSA tested above normal were offered further tests. Over 14 years of follow-up, there were 78 deaths from prostate cancer in the unscreened group and 44 deaths from prostate cancer in the screened group.

According to the study results, every 293 PSA screenings meant one life saved. And one life was saved for every 12 men diagnosed with prostate cancer.

Much of the controversy over PSA testing comes from the uncertainty how to deal with the information the tests provide. Most prostate cancers grow slowly and PSA testing leads to detection of many small, slow-growing tumors that might otherwise never be found. There is disagreement over the best way to treat these small tumors, or whether they should be treated at all, particularly in older individuals.

In essence, PSA tests are a blunt instrument. They can help detect prostate cancer but offer little information on which of the smaller cancers are destined to be dangerous. And without this information, choosing the best way to treat these cancers can be largely guesswork. While the Swedish study can't help with that, it does come down firmly on the side of PSA screenings saving a lot of lives.

Recently revised guidelines from the American Cancer Society recommend that men discuss taking the PSA test with their doctor starting at age 50. Men at higher risk for prostate cancer—African-Americans and men with a family history of the disease—should start this discussion at age 45.

An ahead-of print article on the study was published online by The Lancet Oncology on July 1, 2010.