Verdict out on prostate cancer screening
Prostate cancer screening may save a small number of lives at best, while exposing many more men to side effects of treatment, according to studies in the U.S. and Europe that differed over survival benefit from the tests.
In one, an American research team detected no reduction in deaths with screening. In the other, a European group reported a 20 percent reduction in mortality among those tested for prostate cancer. Both studies, published on the New England Journal of Medicine's Web site, left enough questions about routine screening that Otis Brawley, chief medical officer of the American Cancer Society, said, "only a man can decide with his doctor."
Prostate cancer was the most common malignancy in U.S. men last year with 186,320 new cases, and the second deadliest with 28,660 deaths, according to the American Cancer Society. Blood tests measure prostate specific antigen, or PSA, a protein that rises with age and benign enlargement as well as cancer. Screening showing elevated levels may lead to some slow-growing cancers getting unnecessary treatment that risks impotence.
"These trials don't tell men what to do. It's very disappointing," said Ruth Etzioni, senior investigator at the Fred Hutchinson Cancer Research Center in Seattle, Wash., who wasn't involved in the studies. "There is potentially an upside to screening. There is also a downside. We knew that before."
The U.S. team, led by Christine Berg of the National Cancer Institute, reported results of the Prostate, Lung, Colorectal and Ovarian Cancer Screening Trial in 76,693 men ages 55 to 74 who were tested and followed for an average of 7 years. Half the volunteers received annual screening and the control group received their doctors' usual care. The death rate did not differ between the groups.
The European study observed 162,243 men ages 55 to 69 for an average of 9 years. Half were offered screening every four years. The results found PSA screening reduced the death rate by 20 percent - along with a risk of overtreating the screened patients.
"This is not the final word. We need longer follow-up," said Berg, senior author of the U.S. study and chief of the early detection research group of the National Cancer Institute's Division of Cancer Prevention.
Men face conflicting advice about prostate cancer screening. The U.S. Preventive Services Task Force says there isn't enough evidence to assess the balance of benefit and harm of PSA screening in men younger than 75, and recommends against screening in men 75 and older. The American Cancer Society recommends that screening be offered to men with an average cancer risk at age 50, and men at high risk at 45, with discussion of risks and benefits.
E. David Crawford, a professor of urology at the University of Colorado Health Science Center in Denver and a co-author of the U.S. study, said he thought the results eventually will show the benefits of prostate cancer screening.
"Men should choose to know, and know to choose," he said.
Along with efforts to make PSA more precise, Berg said researchers are pursuing new molecular and genetic tests to sift out lethal cancers from less harmful ones within the next 10 years.