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Value of PSA Screening Questioned

Value of PSA Screening Questioned

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Oct. 3, 2002 -- Nowadays, fewer men die of prostate cancer. Aggressive screening with the PSA test usually gets the credit. But now an interesting natural experiment raises doubts.

This "experiment" happened from 1987 to 1990. Blood tests for prostate-specific antigen (PSA) were just coming into widespread use. Medicare data for men aged 65-79 in those years show that the test was used very aggressively in the Seattle area, but not in Connecticut. More than five times as many men in Seattle got PSA screening. This led to 2.2 times more prostate biopsies and more than six times as many operations to remove the prostate gland.

This should have saved lives. But 11 years later, men in Seattle and Connecticut had the same rate of prostate-cancer death. Study leader Michael J. Barry, MD, is chief of general medicine at Massachusetts General Hospital and associate professor at Harvard Medical School. The findings appear in the Oct. 5 issue of the British Medical Journal.

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"It's not that there was no PSA testing in Connecticut, but there was 5.4 times as much PSA testing in Seattle. We thought the population of Connecticut would pay the price for that, but apparently not," Barry tells WebMD. "It doesn't look like that pretty dramatic difference in intensity of testing made any difference in prostate cancer mortality."

PSA is a protein made by cells of the prostate gland. Blood levels of PSA go up when the prostate is enlarged. Sometimes this means nothing. But sometimes it means cancer. Only a biopsy can tell. Current guidelines from the American Urological Association call for annual PSA screening of all men after age 50. Black men and men with family histories of prostate cancer have a higher risk of the disease. They are advised to begin annual screening at age 40.

Prostate cancers usually -- but not always -- grow slowly. If a biopsy finds cancer, men have four standard options: wait to see if the cancer gets bigger, have surgery, have external-beam radiation treatment, or have tumor-killing radioactive seeds implanted in the prostate. These treatments can have many serious side effects, including impotence and urinary incontinence. Cryotherapy, where freezing temperatures are used to kill cancer cells, is another, less readily available, treatment option.

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Some medical experts ask whether aggressive PSA screening is a good idea. Britain hasn't had an aggressive screening program, yet there's been a drop in prostate-cancer mortality similar to that seen in the U.S. An editorial co-authored by patient advocate Hazel Thornton appears alongside the Barry study. Thornton has received an honorary doctor of science degree for her work to make medical researchers more aware of patient needs. A cancer survivor herself, she questions whether screening is helpful for individual patients.

"As I know from my own experience, when a man goes for a PSA test or a woman for a mammogram, this is a very personal thing," Thornton tells WebMD. "A person applies the result to his or her own health. But a screening program is based on the attempt to produce a fall in mortality for the entire population. These programs don't stress the limitations, risks, or shortcomings of the test itself, or social and financial consequences that accrue from being screened. One goes into screening believing this has got to be a good thing -- after all, the medial profession is offering it to you. But you find it leads you into very tricky waters."

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Most men believe that PSA screening will find cancers earlier and that early treatment will save lives, according to another paper in the same issue of the BMJ. Study leader Ann McPherson, MD, is a primary care doctor who also teaches at the University of Oxford, England.

"This is mainly a group of men who have prostate cancer," McPherson says. "They are most vociferous in saying prostate cancer screening should [be provided by U.K. medical services]."

McPherson lets her own patients know that the PSA test is available. But she tells them about the drawbacks as well as the possible benefits.

"First you need to know it is not a terribly good test in many ways," she says. "It is difficult to interpret the test. It certainly doesn't pick up all prostate cancers, so there is a problem with that. More important is that it diagnoses cancers that would never be very important, and you end up having many investigations and surgeries that aren't necessary."

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But that's not the view of urologist Kenneth Ogan, MD, an assistant professor at Atlanta's Emory University School of Medicine.

"Numerous studies have looked at tumors removed after detection via PSA screening. Upwards of 95% of these have aggressive cancers in them," Ogan tells WebMD. "It makes sense to me that the downward trend in prostate-cancer mortality is from PSA screening. And I'm of the younger generation. You'd get a stronger vote for PSA screening from more experienced urologists who used to see people come in with much more advanced disease, where cure is impossible."

Like Ogan, Barry supports U.S. PSA screening recommendations. Like McPherson, he thinks patients should get full information on the risks as well as the benefits of screening.

"Men aged 45 and older with risk factors or family history of prostate cancer should no doubt avail themselves of PSA testing," Barry says. "Men should know about the risks and benefits of screening and that it is unclear whether early detection of prostate cancer will make them live any longer. I do think people should know the limitations of the evidence."

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