The heated debate about whether PSA testing saves lives is no closer to ending, with the release of two massive studies whose findings contradict one another.

Those in both the pro-PSA testing camp and those opposed have been anxiously waiting the results of these two clinical trials, one out of the U.S. and one out of Europe, both of which were published online Wednesday on the New England Journal of Medicine website.

The U.S. study, called the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial, followed more than 76,000 men. Half were offered annual PSA and digital rectal exams, or both, and half had no screening.

After seven years of follow-up, there were 2,820 cases of prostate cancers in the screening group and 2,322 cancers in the other group. That resulted in 50 deaths in the screening group and 44 deaths in the other.

"The rate of death from prostate cancer was very low and did not differ significantly between the two study groups," the authors concluded.

But another study from Europe study that followed more than 162,000 older men found the opposite result - a 20 per cent reduction in death from prostate cancer among those who had PSA screening.

The European Randomized Study of Screening for Prostate Cancer (ERSPC), the world's largest prostate cancer screening study, offered half the group prostate cancer screening through the PSA test every four years; the rest did not.

The researchers found that for every 1,408 men screened, 48 were diagnosed with cancer diagnosed and received treatment, resulting in saving one life.

Prof. Fritz Schr�der, international co-ordinator of the ERSPC study, says that while the study is ongoing, the initial results suggest that PSA testing saves lives.

"The study shows that PSA screening delivers a 20 per cent reduction in mortality from prostate cancer. This provides decision makers on screening policies with important new data on the effectiveness of PSA testing in preventing deaths."

The authors noted, though, PSA testing led to a high rate of "overdiagnosis"--identifying those cancers that are so small, they likely would never have been detected during the man's lifetime About 30 per cent of the cancers detected were "indolent" or slow growing and therefore not likely to ever cause symptoms or be fatal the authors reported.

A Dutch-led study pointed to that exact problem just last week.

That study found that the proportion of patients overdiagnosed with prostate cancer ranged between 23 per cent and 42 per cent of PSA-detected cancers.

"We have known for a long time that PSAs clearly lead to the over-detection of prostate cancer," Dr. Neil Fleshner, of Princess Margaret Hospital in Toronto, told CTV News last week.

Because of overdiagnosis, too many men suffer needlessly by undergoing further tests or medications that may not help them live longer.

The PSA test detects levels of a substance called prostate specific antigen. Elevated levels may indicate problems, including cancer.

The value of PSA testing has been questioned for some time because of its high rate of false-positives. A false positive result can lead to unnecessary follow-up testing, such as biopsies, or even to surgery that can sometimes leave patients incontinent or impotent.

For these reasons, the test is not offered to the general population nor is it covered by some provincial health plans.

The Canadian Cancer Society has concluded that for men with symptoms of prostate cancer, PSA testing can be an important tool in diagnosing the disease. But for those who do not have symptoms, PSA screening does not appear to save lives, they say.

Dr. John E. Niederhuber, director of the National Cancer Institute, which sponsored the PLCO study, says new tests may soon replace the PSA.

"Clearly, we need a better way of detecting prostate cancer at its earliest stages and as importantly, a method of determining which tumors will progress.

"Many of the molecular studies we're currently sponsoring will hopefully yield new, better ways of definitively classifying which men need treatment and which can consider watchful waiting," he said in a statement.