ProNurse

By Gina Kolata

The P.S.A. blood test, the popular screening test for prostate cancer, saves few if any lives and exposes large numbers of men to risky and unnecessary treatment, two large and rigorous studies have found.

The findings raise new questions about the rapid and widespread adoption of the test, which measures a protein released by prostate cells. It was introduced in 1987 and quickly became a routine part of preventive health care. Experts debated its value, basing their views on data that often involved statistical modeling and inferences.

Now, with the new data, cancer experts said men should carefully consider the test’s risks and benefits before deciding to be screened.

The studies, said Dr. Otis Brawley, chief medical officer at the American Cancer Society, are “some of the most important studies in the history of men’s health.”

For years, the cancer society has urged men to be informed before deciding to have a P.S.A. test. “Now we actually have something to inform them with,” he said. “We’ve got numbers.”

Dr. H. Gilbert Welch, a professor of medicine at Dartmouth who studies cancer screening, also welcomed the new data. “We’ve been waiting years for this,” he said. “It’s a shame we didn’t have it 20 years ago.”

Both reports were published online Wednesday by The New England Journal of Medicine. One involved 182,000 men in seven European countries; the other, by the National Cancer Institute, involved nearly 77,000 men at 10 medical centers in the United States. In both, participants were randomly assigned to be screened – or not – with the test for P.S.A., or prostate-specific antigen. In each study, the two groups were followed for more than a decade while researchers counted deaths from prostate cancer, asking if screening made a difference.

The European data involved a consortium of studies with different designs. Taken together, the studies found that screening was associated with a 20 percent relative reduction in the prostate cancer death rate. But the number of lives saved was small: 7 fewer prostate cancer deaths for every 10,000 men screened and followed for nine years.

The American study, which had a single design, found no reduction in deaths from prostate cancer after most of the men had been followed for 10 years. Every man has been followed for at least seven years, said Dr. Barnett Kramer, a study co-author at the National Institutes of Health. By seven years, the death rate was 13 percent lower for the unscreened group.

The European study saw no benefit of screening in the first seven years of follow-up.

The reason screening saved so few lives, cancer experts say, is that prostate cancers often grow very slowly, if at all, and most never endanger a man if left alone. But when doctors find an early- stage prostate tumor, they cannot tell with confidence if it will be dangerous, so they usually treat all early cancers as if they were life-threatening. As a result, the majority of men, whose early- stage cancers would not harm them, suffer serious effects of cancer therapy but get no benefit. Others, with very aggressive tumors, may not be helped by screening because their cancer has spread by the time it is detected.

Cancer of the prostate is not the only one that is hard to stop with screening. If the European study is correct, mammography has about the same effect as the P.S.A. test, said Dr. Michael B. Barry, a prostate cancer researcher at Massachusetts General Hospital who wrote an editorial accompanying the papers. But prostate cancers often are less dangerous than breast cancers, so screening and subsequent therapy for men can result in more harm.

In the European study, 48 men were told they had prostate cancer, and needlessly treated for it, for every man whose death was prevented. With mammography, about 10 women receive a diagnosis and needless treatment for breast cancer to prevent one death.

Dr. Peter B. Bach, a physician and epidemiologist at Memorial Sloan-Kettering Cancer Center in New York, says one way for a man to think of the data is to suppose he has a P.S.A. test today. It reveals he has prostate cancer, and he is treated for it. There is a 1 in 50 chance that, in 2019 or later, he will be spared death from a cancer that would otherwise have killed him. And there is a 49 in 50 chance that he will have been treated unnecessarily for a cancer that was never a threat to his life or health. Prostate cancer treatment can result in impotence and incontinence when surgery is used to destroy the prostate, and painful defecation or chronic diarrhea when the treatment is radiation.

When the American and European studies began, in the early 1990s, P.S.A. testing was well under way in the United States, and many expected that the screening test would make the prostate cancer death rate plummet by 50 percent or more. Dr. Brawley was at the cancer institute then, though not directly involved with its prostate cancer screening study. But he saw the reactions.

Some urologists said the study was unethical, because some people would not be screened, and demanded that it be shut down, he said. One group of black urologists encouraged black men not to participate because blacks have a greater risk of prostate cancer and it seemed obvious they should be screened.

Some thought that they would see fewer cancer deaths among the screened men in as little as five years. But as the studies continued, it became clear that screening would not have a large, immediate effect – if it did, the studies would have been stopped and victory declared.

Cancer researchers began turning to less rigorous sources of data, with some arguing that screening was preventing prostate cancer deaths and others arguing that it was not.

In the United States, many men and their doctors have made up their minds – most men over age 50 have already been screened . In Europe, according to Dr. Fritz H. Schrder of Erasmus University, the lead author of the European study, most men are not screened. “The mentality of Europeans is different,” he said; screening is not promoted as much.

Originally published by The New York Times Media Group.

© 2009 International Herald Tribune. Provided by ProQuest LLC. All rights Reserved.

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