By Julie Deardorff, Tribune Newspapers
8:38 PM EDT, August 29, 2012
Experts say that a blood test commonly used to screen for prostate cancer can cause more harm than good and leads healthy men to receive useless and sometimes dangerous treatments.
But try telling that to the tens of millions of American men who continue to show up for their annual prostate-specific antigen (PSA) screening, which measures the level of PSA in the blood.
Even with evidence that a PSA test doesn't necessarily improve health for many men — and that treatment prompted by screening sometimes leads to erectile dysfunction, incontinence and bowel problems — research shows men remain fiercely loyal to the test, and doctors keep ordering them.
The stark difference between the recent recommendations made by the U.S. Preventive Services Task Force and public opinion can be partially explained by the power of the anecdote and personal experience, according to a study published in the journal Psychological Science.
"We all know of folks who have had a positive PSA test, had serious treatment and are now cancer-free," said Hal Arkes, the study co-author and a psychology professor at Ohio State University.
What most people don't realize, however, is that a large proportion of those prostate problems would never have caused the man any problems, Arkes said. The task force drew its conclusions after analyzing published epidemiological studies and other data that prove the harms caused by the treatment. The general public is often less knowledgeable of the risk because it doesn't keep up with this type of data, he said.
The PSA test also generates a very large number of false positive results, which can lead to potentially unnecessary prostate biopsies, said Arkes.
"Many people incorrectly believe they have been saved by the PSA test," he said. "These people are pretty angry with the task force (for recommending against PSA tests), not knowing that they are in the 'harms but no benefits' category."
Many alternative screening tests are being studied, but so far there are no blockbusters, or anything close, on the horizon, said Scott Eggener, associate professor of urological oncology at the University of Chicago.
And some say that if there is no better alternative, PSA screening is better than nothing. Paul Cooper, 59, had no symptoms, but his increasing PSA level was picked up through yearly screenings, which he started at age 50. After seeking a second opinion, Cooper underwent a biopsy and prostatectomy last fall; he is now cancer-free.
"My doctors were adamant PSA is effective," said Cooper, of Hope, N.J. "Both said if I hadn't had a PSA, I wouldn't have shown symptoms for seven or eight years; by that time it would have spread. That's why I recommend PSA screening to friends and guys I work with."
Stories and anecdotes are often more vivid and compelling than a set of dry numbers, which might be one reason why people tend to dismiss scientific evidence in favor of personal experience. University of Michigan research has also shown people are more likely to pick a treatment if they have read success stories from other patients.
Some data shows that people are more likely to recommend treatment to others if a close relative or trusted source received it, even if the evidence showed it only worked for a minority of people.
One drawback with personal experience, however, is that it can't include what would have happened if a screening test or treatment had not been given, Arkes said.
"While people only experience what happened to them, the task force can use data to balance not just what happened but what could have happened if they hadn't been given the test," he said.
In fact, the task force found that those not given the PSA test had just as many deaths as those who took it, but the former group had fewer side effects.
The intense debate over the trade-offs between the benefits and harms of screening flared in 2008, when the task force recommended against screening for prostate cancer in men 75 years or older. These guidelines were widely ignored, as nearly half of men in that age group continued to get screening tests, according to research published in the Journal of the American Medical Association.
Meanwhile, another study published in JAMA showed that screening attracts the wrong populations.
"The guys who are young and healthy and have the most to gain are screened at a lower rate than the old, sick guys with nothing to gain and potential harm," said Eggener, co-author of the JAMA studies.
Earlier this year, the task force broadened its recommendation to discourage PSA screening for men of all ages.
They concluded the current evidence is "insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality or conflicting, and the balance of benefits and harms cannot be determined."
For younger men, the available data "strongly suggests that PSA screening can save lives and, without a doubt, it has," said Eggener. Over the last two decades, the U.S. age-adjusted mortality rate from prostate cancer has decreased 40 percent.
"The decreasing death rate from prostate cancer is a great public health success story," Eggener said. "But you can't talk about that improvement without discussing the large number of men treated for prostate cancer that would never have otherwise caused them symptoms or problems during their life span."
A more sensible approach is to talk about the pros and cons of PSA screening and consider screening for men with a life expectancy of more than 8 to 10 years, since they are most likely to benefit, Eggener added.
Traditionally, nearly all men diagnosed with prostate cancer were treated, regardless of age or health.
Clinical research has shown, however, that not all prostate cancer needs to be treated aggressively or immediately after the diagnosis. A landmark study, for example, found that surgery is unneeded for most early-stage prostate cancer. Most men with this early-stage cancer will live just as long by monitoring their cancer, according to the study, published in the July edition of the New England Journal of Medicine.
At one time, the doctors who promoted this "active surveillance" strategy were considered fringe or renegade, but it has become increasingly common, Eggener said.
"It's not for every patient, but for appropriately selected patients it's a reasonable management strategy," he said.
It definitely wasn't for Cooper, who worried that his cancer would spread.
"Personally, if I have cancer in me, I don't want to let it go," he said. "I'd rather be proactive and take care of it than sit back and wait."
Eggener agreed that "PSA may indeed save your life." But he also cautions that men need to be aware of the possibility of being diagnosed with a cancer that will never cause symptoms or kill them.
What you can do
Read the review on prostate cancer at uspreventiveservice staskforce.org. Tell your doctor you've read it, and consider testing only if your risk is sufficiently high, suggested Hal Arkes, who studies why men continue to seek out the PSA even as controversy swirls around its worth.
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