A new study suggests that screening men with the prostate-specific antigen (PSA) test doesn't improve survival rates for prostate cancer, further muddying the already complicated debate over how hard to look for signs of the disease. Many health organizations recommend that the test—which looks at levels of a protein that sometimes, but not always, indicates cancer—be offered to all men over 50; others are waiting for strong evidence of its effectiveness. So far, studies have been inconclusive. The latest, which appears in this week's Archives of Internal Medicine, recommends that men learn about the pros and cons of the test and then decide whether to get it.

Researchers looked back at the medical records of 501 men diagnosed with prostate cancer who died of the cancer or of any other cause. They compared the men's experience with that of men still living who were the same age and received similar access to care. They were looking to see which men had been screened for prostate cancer with the PSA test. If the test made a difference in survival, it would make sense that more of the men still alive had been screened. In fact, the authors found that 14 percent of the men who had died were screened, compared to 13 percent of the men who were living. The results suggest that even if the PSA test succeeds in picking up prostate cancer earlier, it doesn't necessarily lead to longer survival.

This study comes on the heels of another, published last summer, which found that men screened with the PSA test had a significantly lower risk of developing metastatic prostate cancer, the most serious form of the disease. The seeming contradiction may be explained by the fact that, while no one would want to have metastatic cancer, survival rates are improving; a significant number of men in whom the disease has spread would still go on to live for years and die of something else, says Michael Barry, chief of general medicine at Massachusetts General Hospital in Boston and author of the editorial accompanying the study.

The debate is important because having the test isn't a risk-free proposition; it finds many slow-growing cancers that would never have caused problems. Many men who go through invasive biopsies, painful surgery, and unpleasant side effects like impotence would probably have died of something else had their cancer never been found. Meantime, the test also fails to pick up cancer in a significant number of people. Barry notes in his editorial that both studies agree a different kind of trial is needed to settle the question of "whether early detection of prostate cancer with PSA screening does more good than harm." Results from two large randomized trials will likely be available in 2009, he says.

John Concato, of the Veterans Affairs Connecticut Healthcare System and Yale University and lead author of the new study, believes that until the question is more conclusively settled, men should seriously consider the pros and cons of the test before having it. In the meantime, he's interested in how best to distinguish between the most serious forms of prostate cancer—which need treatment—and the types that could be monitored but left untreated.

To find out more: The U.S. News guide on prostate cancer gives in-depth information about symptoms, tests, treatment, and prevention.