Study Shows Prostate Cancer Test’s Accuracy
The blood test for prostate cancer predicted almost three-quarters of the malignancies that developed within four years among thousands of middle-age and elderly men, a study found.
The test had few false positives, wrongly indicating that malignancies were present in only 9% of cancer-free men, researchers said in today’s issue of the Journal of the American Medical Assn.
The study underscores the value of the test, experts agree, but does not settle the most important question: Will screening older men with the test lower the death rate from prostate cancer?
Prostate-specific antigen screening, or PSA, is controversial because it has led to almost a sixfold increase in the number of surgical prostate removals.
Such surgery often makes men impotent or incontinent and may not lengthen their lives, especially if they are elderly and the cancers are slow-growing. No study has yet shown that screening leads to greater cancer survival rates.
Dr. Peter H. Gann, lead author of the study, said a large new clinical trial is needed to learn whether yearly PSA screening reduces death rates. The National Cancer Institute recently began such a trial with 37,000 men.
For now, patients will have to wrestle individually with what kind of screening to seek. The American Cancer Society and American Urological Assn. recommend that all men over 50 get yearly PSA screening and a finger rectal exam, Gann said.
The government has not made any recommendation about the use of PSA, though the Food and Drug Administration gave approval last August for using the test to detect the nation’s second-leading cancer killer of men.
In the study, blood samples collected and frozen from 14,916 men ages 40 to 84 in 1982 were tested more than a decade later for PSA, a protein that cancerous prostate glands produce in excess. PSA results were then compared with whether the men had been diagnosed with prostate cancer from 1982 to 1992.
The test predicted 73% of the cancers--and 87% of the fast-growing cancers--that were diagnosed within four years of the study’s start.
