The PSA prostate cancer screening test saves lives, a new study shows.

For men with no symptoms of prostate trouble, PSA screening cuts the risk of deadly metastatic prostate cancer -- cancer that spreads through the body -- by 35 percent.

The finding comes from a study comparing 236 men with metastatic prostate cancer with 462 age-matched men without metastatic cancer. University of Toronto researcher Vivek Goel, MD, and colleagues report the findings in the August issue of The Journal of Urology.

"If this is the benefit PSA testing provides, it is going to warrant the risks involved for most men," Goel tells WebMD. "In young men with no risk factors, PSA testing may not be indicated, even at this level of benefit. For men over 50, I think it will be. And for younger men with a family history of prostate cancer or other risk factors, it will be indicated."

Read WebMD's "How to Lower Your Risk of Prostate Cancer"

PSA Debate

PSA -- prostate specific antigen -- is a chemical marker made only by cells of the walnut-sized prostate gland. The first sign of prostate cancer can be a spike in blood levels of PSA. A regular PSA test can detect early prostate cancer.

But the test is controversial. Low PSA levels don't necessarily mean a man is cancer-free. And high PSA levels don't necessarily mean a man has dangerous prostate cancer. Nevertheless, many American men get regular PSA tests -- which go hand in glove with digital rectal exams -- to screen for early prostate cancer.

Unfortunately, PSA test results remain a matter of interpretation. Doctors tend to refer men for prostate biopsy if they have a PSA score of 4 or more. But that cutoff is arbitrary -- and not particularly meaningful, says Charles A. Coltman Jr., MD, associate chairman for cancer control and prevention of the Southwest Oncology Group in San Antonio.

In this week's issue of The Journal of the American Medical Association, Coltman and colleagues reported the results of a study of some 8,600 men who underwent PSA testing. All the men in the study agreed to have a prostate biopsy -- whether or not they had a high PSA score.

"It was astonishing," Coltman says. "We found individuals with prostate cancer at every range of PSA --from 4 down to 0.1. And a substantial number of them had high-grade prostate cancer. In fact, some of these cancers were in men who had gone through seven years of PSA and digital rectal exams and were found to be normal in all respects."

Read WebMD's "Prostate Cancer: Symptoms to Look For"

What's a Man to Do?

The American Cancer Society recommends annual PSA tests and digital rectal exams for all men over 50. Men in at high risk -- blacks and those with a family history of prostate cancer, may consider annual prostate cancer screening at age 45 or younger.

Even though he's not blind to its faults, Coltman says that men should discuss PSA testing with their doctors.

"I don't think one should dissuade a man from prostate screening, because in fact the screening may show the PSA is elevated and his prostate gland is abnormal," he says. "But doctors must understand that we are going to rewrite the book. Because if PSA is less than 4 or even less than 2.5, you cannot be totally confident there is not a problem."

Coltman suggests that current PSA cutoff levels may be appropriate for men not at high risk. For those in high-risk groups, he suggests that doctors seek biopsies when they detect prostate abnormalities -- even if a patient's PSA is below the current cutoff.

Deciding on prostate cancer screening is a matter of weighing the benefits against the risks. The benefit: catching a deadly prostate cancer while it is still curable; the risk: unnecessary biopsy and, perhaps, surgery or radiation therapy for cancer that would never have been a problem if it hadn't been detected.

Large studies are under way to help men make this difficult decision. But results won't be available for a long time.

"We don't expect results before the end of this decade -- or well into the next decade," Coltman says.

Read WebMD's "Cancer Prevention: What Really Works?"

By Daniel J. DeNoon, reviewed by Brunilda Nazario, MD

SOURCES: Kopec, J.A. The Journal of Urology, August 2005; vol 174 (pre-publication copy). Thompson, I.M. Journal of the American Medical Association, July 6, 2005; vol 294: pp 66-70. Vivek Goel, MSc, MD, FRCPC, professor, public health sciences and health policy management and evaluation, University of Toronto, Ontario. Charles A. Coltman Jr., MD, associate chair, cancer control and prevention, Southwest Oncology Group, San Antonio.