The study of about 1,000 men in New England is not the final word on the subject. But it bolsters the opinions of those in the medical community who have argued that men should be informed of the uncertainty and the potential risks of the PSA screening test, rather than simply advised to get tested.

"The bottom line is we still don't know whether PSA [testing] does more good than harm," said Dr. Michael Barry of Massachusetts General Hospital, who was not involved in the study.

Little Evidence Tests Improve Survival

Prostate cancer strikes more than 230,000 U.S. men a year, and more than 30,000 die of it.

Doctors can screen healthy men for the disease by measuring the level of PSA (prostate-specific antigen) in their blood and by performing a digital rectal exam. However, there is little evidence that these tests reduce mortality.

In the new study, Dr. John Concato of the Veterans Affairs Connecticut Healthcare System and Yale University addressed the question of whether screening improves the chances of survival. Out of some 72,000 veterans receiving care at any of 10 VA medical centers in New England, he identified 501 men who were diagnosed with prostate cancer between 1991 and 1995 and died before the end of 1999.

He also identified a comparison group of 501 veterans who were alive when the corresponding patient died. The "controls" were a representative sample of the men in the community, matched for age and VA facility to the "cases."

Concato and his colleagues then reviewed medical records to determine whether the men had received PSA tests or physical exams before any suspicion of prostate cancer arose. They reasoned that, if screening tests improved survival, fewer of the men who died would have been screened compared with the men who were living.

They found that virtually the same percentage of men in each group had received screening tests. The researchers concluded that screening did not reduce mortality, whether men got PSA tests alone or also had rectal exams.

"Based on available evidence, including the present study, recommendations regarding screening for prostate cancer should not endorse routine testing of asymptomatic men to reduce mortality," Concato concluded. "Rather, the uncertainty of screening should be explained to patients in a process of `verbal informed consent,' promoting informed decision making."

'Substantial Downside'

In an editorial, Barry said PSA screening is known to have a "substantial downside," including false alarms, unnecessary biopsies and anxiety.

Most men with elevated PSA scores don't have prostate cancer. At the same time, up to 30 percent of men who actually have prostate cancer have normal PSA scores.

In addition, surgery and radiation for prostate cancer sometimes cause impotence or incontinence.

Advocates of screening argue that mortality has declined in recent years.

"The death rate from prostate cancer is coming down," said Dr. Robert Nadler, associate professor of urology at Northwestern University. "I think really the best explanation for that is aggressive PSA screening and treatment."

But Dr. Barnett Kramer of the National Institutes of Health pointed out that more effective therapies came into use about the same time that PSA testing became available. "That would lead you to believe mortality should be falling, regardless of screening," he said.

The only way to tell for sure whether prostate cancer screening saves lives is to conduct a controlled experiment with thousands of men in which half are randomly assigned to be screened and the other half aren't. The men would then be followed to see if there are fewer deaths in the screened group.

Such a trial is now going on, Kramer said, and results will be known in a few years.