MONDAY, Oct. 25 (HealthDay News) -- Having a prostate-specific antigen (PSA) test to screen for prostate cancer reduces the risk that if cancer develops it will spread to other parts of the body, new research indicates.

The finding adds to the ongoing debate on whether PSA screenings actually improve survival rates or, by contrast, lead to unnecessary treatment.

"Our study shows that routine screening not only improves the patient's quality of life by stopping metastatic disease, but it also decreases the burden of care for this advanced disease that must be provided by the health-care system," study author Chandana Reddy, a senior biostatistician at the Cleveland Clinic in Ohio, said in a news release from the American Society for Radiation Oncology.

"This demonstrates that the PSA test is extremely valuable in catching the disease earlier and allowing men to live more productive lives after treatment," Reddy said.

Reddy and his colleagues are to report their findings Monday at the American Society for Radiation Oncology annual meeting, in San Diego.

PSA tests are blood tests that have been available and widely used since 1993. They measure levels of the prostate-specific antigen protein produced by the prostate; high levels are thought to be an indication of prostate cancer.

However, critics have cautioned that some patients diagnosed with early prostate cancer are subjected to aggressive treatments -- and their unwelcome side effects, such as incontinence and erectile dysfunction -- for a disease that is often slow-moving and of no real consequence to survival if left untreated among older patients who are likely to die of other, unrelated causes.

The researchers pointed out that prostate cancer is not curable when it is caught late and has spread (or metastasized) to other parts of the body. They suggested that assessing to what degree a PSA diagnosis might reduce the risk of metastasis could be the best way to determine the value of the test.

To that end, Reddy and his team analyzed data on more than 1,700 prostate cancer patients who between 1986 and 1996 had been treated with either radiation therapy or surgery to take out their prostate gland and the surrounding tissue.

Noting that in the first half of the study period, PSA tests were not yet available, the authors compared the spread of the disease over the course of 10 years among those who had been diagnosed with a PSA test and those who had not.

Over the 10-year period, metastatic disease took hold among 13 percent of all the patients. However the researchers found that regardless of whether patients were categorized as having high-, medium-, or low-risk disease, those who had been diagnosed as a result of a PSA screening were significantly less likely than those who weren't to have seen their cancer spread during the decade following their original treatment.

It should be noted that studies presented at scientific meetings do not face the same peer-review scrutiny as those published in reputable journals.

Dr. Lionel L. Banez, an assistant professor of urologic surgery at Duke University Medical Center, said that the current study leans toward the relative benefits of prostate cancer screening.

"There is compelling evidence that PSA testing saves lives, especially when performed in an optimized strategy," he said. "For example, getting an initial PSA measurement at age 40 to properly assess baseline prostate cancer risk has been proven to be quite beneficial.

Nevertheless, Banez acknowledged that doctors need to interpret test results judiciously.

"The challenge," he stressed, "lies in ensuring that the risks for over-diagnosis and over-treatment, as well as potential decline in quality of life, are minimized or avoided."

More information

For more on prostate cancer, visit the National Cancer Institute.