Two widely used tests for prostate cancer failed to save lives in a new study, adding to the debate over whether men should be screened for the disease.
The study was small — only 1,002 men — and will not be the final word on the issue. But it may hint at what lies ahead when the results of two large studies of prostate cancer screening appear in a few years.
The researchers looked at two screening tests that are performed millions of times a year in the United States: a blood test that measures prostate specific antigen, or PSA, and a digital rectal exam, the rubber-glove test in which a doctor feels for abnormalities in the prostate through the rectal wall.
Study co-author Dr. John Concato, a clinical epidemiologist at the VA Connecticut Healthcare System, said that for now, doctors should tell men that screening tests for prostate cancer are not perfect, and men should decide for themselves whether to get screened.
Doctors have long known that some cases of prostate cancer can be so slow-growing that they never causes symptoms, much less death. In addition, surgery and radiation treatment for prostate cancer can cause incontinence and impotence. So for some men, detecting prostate cancer early through screening can do more harm than good.
In addition, the PSA tests can yield ambiguous results. Most men who undergo a biopsy because they have elevated PSA levels do not have prostate cancer. And some men with low PSA levels do have cancer.
Medical organizations differ on their screening recommendations. But generally, most say men should be told the risks and benefits of screening first.
“We should tell patients about the uncertainty,” said Dr. Howard Parnes of the National Cancer Institute. “All too often we behave as if we know screening is a good thing.”
In the study, published in Monday’s Archives of Internal Medicine, researchers compared two groups of men treated at 10 Veterans Affairs medical centers.
One group consisted of 501 men who were diagnosed with prostate cancer and later died of that disease or other causes. Researchers chose 501 men who matched the first group for age and other factors, but who remained alive.
The researchers found that the men who were alive were no more likely to have been screened than the men who died of prostate cancer. The study was based on data from 1991 through 1999, the early years of PSA screening.
The American Cancer Society says men starting at age 50 should be informed of the risks and benefits of screening, then make their own decisions, but higher-risk men, including blacks, should be screened annually starting at age 45.
The prostate is a gland the size of a walnut under the bladder that makes fluid for semen. Prostate cancer is second only to skin cancer in its prevalence among American men.
More than 232,000 U.S. men are expected to be diagnosed with it this year and about 30,000 will die of it. A diet high in fruits and vegetables may reduce the risk.
For now, cancer experts must wait until 2009 for better answers. That is when results are expected from large studies of the PSA test in nearly 300,000 U.S. and European men.
And if the large trials show little benefit from screening?
“It would certainly create a great deal of chaos,” said Dr. Durado Brooks, director for prostate cancer at the American Cancer Society.