March 18, 2009 -- Interim findings from an eagerly awaited ongoing government study show no evidence of a survival benefit associated with aggressive screening for prostate cancer using the prostate specific antigen (PSA) test.
More prostate cancers were detected over an average of seven years of follow-up among men who had regular PSA testing in addition to digital rectal exams compared to usual care, which could have included screening. But the increase in prostate cancers did not translate into fewer deaths from the disease.
The findings are certain to add to the controversy surrounding the value of PSA testing for prostate cancer screening, and the debate about whether current screening practices have led to overdiagnosis and overtreatment of prostate cancer.
The study, funded by the National Cancer Institute was published online ahead of publication in the March 26 issue of the New England Journal of Medicine.
"What this report tells us is that there may be some men who are diagnosed with prostate cancer and have the side effects of treatment, such as impotence and incontinence, with little chance of benefit," NCI director John E. Niederhuber, MD, says in a news release.
"Clearly, we need a better way of detecting prostate cancer at its earliest stages and as importantly, [we need] a method of determining which tumors will progress."
Screening Beneficial in European Study
To add to the confusion, findings from a major European trial appearing in the same issue of the New England Journal of Medicine did show a modest, 20% survival benefit associated with PSA screening in men followed for an average of nine years.
Both the U.S. and the European studies will be presented this week at the European Association of Urology annual meeting in Stockholm, Sweden.
For every 10,000 men screened with PSA over a nine-year period in the European trial, seven fewer deaths from prostate cancer were reported.
But the European researchers estimated that 48 additional men whose cancers were detected as a result of screening would need to be treated to avoid one prostate cancer death.
That compares with about 10 additional treatments among women screened with mammography needed to prevent one death from breast cancer, prostate cancer screening researcher Michael J. Barry, MD, of Harvard Medical School tells WebMD.
Barry, who wrote an editorial that appeared with the studies, adds that the new research helps to quantify the benefits and risks associated with PSA screening.
"When you look at the two trials together it becomes clear that the benefits, in terms of survival, are fairly modest," he says. "They are similar to what we see with mammography, but in my opinion it comes at a much higher price in terms of overdiagnosis and overtreatment."
Longer Follow-up May Be Needed
NCI researcher Christine D. Berg, MD, tells WebMD the failure of the U.S. trial to show a survival advantage associated with PSA testing could be due to the relatively short follow-up.
The researchers plan to follow the almost 77,000 men participating in the trial for a total of 17 years, and the men in the PSA arm of the trial will continue to have annual screenings.
Berg points out that in the European study the survival advantage was not seen until after seven years of follow-up.
But she echoed Barry's concerns that costs of PSA screening in terms of increased treatment may not be justified by the benefits.
"Personally, I think we should do some screening, but we really can't say what the optimal screening protocol should be at this time," she says. "The best we can do is counsel men to talk to their physicians."
Current Screening Recommendations
The U.S. Preventive Services Task Force, which makes recommendations about health care screenings, recently concluded that there is insufficient evidence to determine if the benefits of prostate cancer screening outweigh the risks in men younger than 75.
Prostate cancer screening is not recommended for older men.
The American Cancer Society does not support routine prostate cancer screening, but the group does urge men who have an average risk for the cancer, beginning at age 50, to talk with their physician about the pros and cons of screening. These discussions should take place at age 45 for men at higher risk.
"I think you will have a lot more men having this discussion with their health care providers as a result of these studies, and from our point of view that is a good thing," American Cancer Society Deputy Chief Medical Officer Len Lichtenfeld, MD, tells WebMD.
Lichtenfeld says the studies are likely to lead to vigorous debate within the medical community about the value of PSA screening.
"For years we've been saying wait for the trials, but so far the trials have not given us a definitive answer about whether prostate cancer screening is beneficial or harmful," he says.
"I suspect there will be a substantial amount of discussion over the next few weeks and months among the experts to try and put these findings into perspective and try and tease out what the message should be."