The two studies can't be compared directly, Andriole said, largely because of differences in their designs. And neither answers the question: Is PSA screening worthwhile?
Dr. Christine Berg, a National Cancer Institute leader of the U.S. trial, said the problem is that while the PSA test can help diagnose prostate cancer, it can't single out the aggressive tumors that will eventually be fatal. The standard statement among doctors is that more men die with their prostate cancer than of it, and no current test can tell a slow-growing, not-dangerous tumor from an aggressive killer.
One recent study found that as many as two of every five men diagnosed with prostate cancer by a PSA screening test had tumors that were too slow-growing to ever be a threat.
"There is no test right now that can be done on blood or urine that will determine how aggressive a tumor is," said Dr. Edward P. Gelmann, professor of oncology at Columbia University Medical Center in New York City. "We're pretty good at identifying very aggressive tumors or very indolent tumors, but there is a large grey area."
"That kind of advance might be just around the corner," Berg said. "I do think we are making strides toward understanding the genetics of prostate cancer. The pace and rapidity with which we will get those answers is improving."
Meanwhile, men who have surgery or other treatments for nonaggressive prostate cancers face such problems as impotence and incontinence.
The death rate from prostate cancer in the United States has been dropping steadily since the early 1990s, when the PSA screening test was first introduced, Gelmann said, but there have been major improvements in treatment si
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