Aug. 31, 2009 -- The PSA prostate cancer screening test does more harm than good, a new study suggests.
How much harm and how much good?
"For every man who avoids a prostate cancer death due to PSA screening, about 50 men have to be treated unnecessarily -- and a third of these men will have serious problems with treatment," study co-author H. Gilbert Welch, MD, MPH, tells WebMD.
Although vast numbers of men undergo annual PSA blood tests, many professional groups, including the American Cancer Society, do not recommend routine PSA screening for prostate cancer. They instead recommend the test only for men who still want it after carefully discussing the risks and benefits with their doctor.
The PSA test became popular in 1986. What have we learned about the test's risks and benefits?
To find out, Welch, professor or medicine at Dartmouth University, and urologist Peter C. Albertsen, MD, of the University of Connecticut, analyzed data on prostate cancer collected by the National Cancer Institute and population data from the U.S. Census.
The result: From 1986 to 2005, PSA testing resulted in the diagnosis of about 1.3 million prostate cancers that would never otherwise have been detected. More than 1 million of these patients were treated with surgery or radiation.
Over that time, deaths from prostate cancer declined. Taking a conservative approach, Welch and Albertsen assumed that PSA detection of early prostate cancers -- and not improvements in treatment -- was responsible for the entire drop in prostate cancer deaths.
In that case, PSA testing would have saved about 56,500 lives. But some 943,500 men would have been "overdiagnosed."
"The overdiagnosed patient is one not destined to experience symptoms or death from the cancer," Welch says. "This means people who were never going to get a dangerous cancer get treated and suffer the ill effects of needless treatment. Overdiagnosed patients cannot benefit from treatment because there is nothing to be fixed, but they can be harmed."
PSA Benefit Smaller Than Supposed
In an editorial accompanying the study, Otis Brawley, MD, chief medical officer of the American Cancer Society, notes that two recent clinical trials of PSA screening argue against routine use of the test. A U.S. trial found no benefit; a European trial found some benefit but a very high rate of overdiagnosis.
The main problem, Brawley says, is that many early prostate cancers never will cause problems. Although PSA tests lead to prostate biopsies that find early prostate cancers, there's still no way to know which of these cancers are dangerous and which aren't.
Yet it's still common for men to be urged to get PSA tests by those who extol the benefits without ever mentioning the risks. They often learn of those risks long after they've undergone costly and adverse event-prone treatment.
"Many men who thought their lives were saved by being screened, diagnosed, and treated for localized prostate cancer are perplexed to learn that so few benefit," Brawley notes.
Watchful Waiting for Prostate Cancer
What if a man decides to get regular PSA tests, but does not undergo treatment if a low-risk cancer is detected?
That's a strategy called watchful waiting. It's more common in Europe than in the U.S. The basic strategy here is to defer surgery or radiation therapy and to have one's doctor keep a close eye on lower-risk prostate cancers.
Can it work? Martin Sanda, MD, director of the prostate cancer center at Beth Israel Deaconess Medical Center, and colleagues evaluated 342 men who deferred treatment for at least one year after prostate cancer diagnosis.
Half the men remained untreated for nearly eight years; the other half eventually opted for treatment an average four years after diagnosis. These men were compared with men who chose immediate treatment after diagnosis.
"Among those who held off on treatment, 98% survived. With immediate treatment, the rate of survival was 99%," Sanda tells WebMD. "That tells us the guys who held off treatment, if there was any downside in terms of prostate cancer survival, it was very small."
Sanda agrees that PSA screening "is a double-edged sword."
"Our study points to one possible way to have your cake and eat it too: If you have PSA screening and treat aggressive cancers, you get survival benefit -- but if you're more selective about when to treat, you lower your risk," he says. "If men and their doctors don't jump to the conclusion that every prostate cancer has to be treated, we can mitigate the problem."
For these reasons, Welch says watchful waiting is not a way out of the dilemma.
"These men have already taken a hit: They've been told they have a diagnosis of prostate cancer," he says. "By the time you are told you have prostate cancer, you are all nervous, you have already lost some sense of well-being. The real issue is, do you want to play this game?"
The Welch/Albertson study, and the Brawley editorial, appear in the Aug. 31 online issue of JNCI: Journal of the National Cancer Institute. The Sanda study appears in the Aug. 31 early online issue of the Journal of Clinical Oncology.