Bad Science: Late-Breaking News
As Discovery went to press, a group of scientists issued a disturbing report. The United States Preventive Services Task Force (USPSTF) recommended against PSA screening for prostate cancer, based on its evaluation of evidence of both benefits and harms. To understand this recommendation, you need to know that the panel is made up of "independent scientists who are better able to objectively evaluate the literature without bias." No urologists were invited to participate.
The panel said that "healthy" men don't need PSA screening. In effect, this decision sets the clock back to before the 1990s, when "healthy" men were diagnosed with cancer that was palpable and often, too late to cure. Is this about progress, or saving money?
Prostate cancer is the most common cancer in American men and the second most common cause of cancer death. Because the cancer begins on the prostate's outer edges, it produces no symptoms until it is far advanced and too late to cure. You can be a "healthy" man and have a steadily climbing PSA, silently trumpeting the danger alarm. Early diagnosis is everything. It is the cornerstone that has dramatically reduced death and suffering.
In 1991, before PSA testing was in place, 20 percent of men were diagnosed with prostate cancer that had already spread to their bone. Today that number is less than 4 percent. It's hard to imagine now, but in 1991, one out of fi ve men had metastases. Today, it's one out of 25.
The effect on deaths is equally dramatic. Between 1994 and 2004, prostate cancer deaths plummeted 40 percent - more than for any other cancer in men or women. But what would have happened if PSA testing and effective treatment had not come along? Using the age-adjusted death rate from 1990 of 39.2 prostate cancer deaths per 100,000 men and applying it to 2007, there would have been 59,000 deaths. Instead, because the death rate fell to 23.5, there were 35,000 deaths. Thus, 24,000 fewer men died from prostate cancer. Because advances in treatment have also played a role, scientists from the National Cancer Institute estimate that 40 to 70 percent of this reduction is the direct result of screening.
Unfortunately, the USPSTF never mentions these figures, and makes no attempt to reconcile them with its recommendations. The scientists did use large, uncontrolled observations to look at the complications of surgery - but not at the number of lives saved since PSA testing was introduced in the United States in the early 1990s. Also, the USPSTF recommendations are based on two trials with only seven and nine years of follow-up - even though it is widely accepted that men with a lifespan of fewer than 10 years should not be screened or treated.
|You can be a “healthy” man
and have a steadily climbing
PSA, silently trumpeting the
danger alarm. Early diagnosis is everything. It is the cornerstone that has dramatically reduced death and suffering.
Of course, there can be harm with any intervention. We can reduce the potential risks of PSA testing by: screening frequently the men who are likely to benefi t the most (younger men with higher or rising PSA levels); screening infrequently, or not at all, men who are older, in poor health, or who have lower PSA levels; using surveillance, not immediate treatment, more often for selected men. Finally, PSA testing should continue to be used for monitoring patients after treatment for prostate cancer, to identify progressive disease.