Prostate Test Misses Tumors, Study Finds
Excerpt By Gene Emery, Reuters Health

The widely used PSA blood test, designed to look for early signs of prostate cancer, misses 82 percent of tumors in men under 60, according to a study released.

The prostate-specific antigen test missed 65 percent of cancers in older males, the study, published in the New England Journal of Medicine, found.

Dr. Rinaa Punglia of Harvard Medical School and her team said the accuracy of the test has been overrated because doctors do not routinely confirm what seems to be a healthy reading on the test.

Currently, a PSA level of 4 or under is considered healthy.

The American Cancer Society says a level above 4 but less than 10 means a 25 percent chance of having prostate cancer. If the level goes above 10, the cancer risk is more than 67 percent.

Punglia's team recommended lowering the "healthy" reading to 2.6 -- even though many more men who do not have prostate cancer will have to undergo painful biopsies to verify they do not have cancer.

The PSA test, approved in 1986, measures levels of prostate-specific antigen, a protein produced by prostate cells and over-produced by prostate tumors. The test has been credited with detecting prostate cancer in its early stages 80 percent of the time.

But the Punglia team evaluated 6,691 volunteers at the Washington University School of Medicine in St. Louis and found that men under 60 with prostate cancer had a "healthy" PSA reading 82 percent of the time.

Only 2 percent of men get a "false positive" -- meaning they have a PSA of above 4 even though they do not have cancer.

For older men, the test missed 65 percent of the tumors and was wrong in 12 percent of the men who had a suspicious reading of 4.1 or above.

Lowering the "healthy" threshold to 2.6 would catch more tumors, the researchers said.

For men under 60, that would double the tumor detection rate to 36 percent, while the ratio of healthy men who would be subjected to an unnecessary biopsy would rise from 2 percent to 6 percent.

The Prostate Cancer Coalition said it already advocates checking men with lower PSA levels.

"While small fluctuations in the PSA reading for men over 60 can be often be a sign of a false positive, those same small changes in younger men can often be a sure sign of cancer," coalition spokesman Jamie Bearse said.

"The National Prostate Cancer Coalition uses a 2.5 PSA rating as the bar for men under 60," he added. "While the study is encouraging, NPCC would suggest that the reading of 2.5 be set even lower, a 2.0, for African-Americans under 60 because black men are at greater risk for the disease."

But in an editorial in the Journal, Fritz Schroder and Ries Kranse of the Erasmus Medical Center in Rotterdam, Netherlands, said there was no conclusive evidence showing the PSA screening test actually reduces the risk of death from prostate cancer without reducing a man's quality of life.

Prostate cancer is usually a slow-growing cancer and often does not require any treatment. However, prostate cancer kills about 29,000 Americans each year and is the second most common cancer killer of U.S. men, after lung cancer.

Reference Source 89

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