TORONTO - A national task force that produces guidelines for doctors says PSA testing should not be used to screen men for possible prostate cancer because it can lead to more harms than benefit.
In guidelines issued Monday, the Canadian Task Force on Preventive Health Care says prostate specific antigen, or PSA, testing is not an effective screening tool because it often produces false-positive results that lead to unnecessary treatments and potentially adverse side-effects.
That conclusion brought swift and mostly negative reaction from some medical and advocacy groups, which disagree with the task force's recommendation that PSA testing be eliminated as a screening tool for prostate cancer.
PSA is a protein produced in the prostate, the walnut-sized gland located below a man's bladder. Elevated levels of PSA in the blood may indicate the presence of prostate cancer.
"Our recommendation is against PSA screening," said Dr. Neil Bell, who heads the working group on prostate cancer screening for the 14-member task force established by the Public Health Agency of Canada.
"We have a stronger recommendation for men over 69 and under 55, and a little less strong recommendation for men between 55 and 69," said Bell, noting that the advice is based on a review of large international clinical trials that compared outcomes for men who got PSA screening and those who didn't over more than a decade.
The evidence suggests that among men aged 55 to 69, almost one in five had at least one false-positive PSA test, and about 17 per cent ended up with unnecessary biopsies of the prostate as a result, Bell said from Edmonton, where he is a professor of family medicine at the University of Alberta.
Furthermore, more than half of detected prostate cancers are overdiagnosed — meaning they won't cause symptoms or death during a man's lifetime. Such overdiagnosis often leads to treatments that can cause impotence, incontinence, infection and bleeding.
"So what's the benefit in that age group? If you screen men based on the protocol in those trials, every two to four years for 13 years, five out of 1,000 will die from prostate cancer. If you don't screen, six out of 1,000 men will die from prostate cancer," Bell said. "So the reduction in prostate cancer mortality is one in 1,000 or about 0.1 per cent."
"To get the benefit, you're diagnosing about 27 or 28 men with prostate cancer who would never benefit from the treatment related to prostate cancer because they would never suffer any difficulty from it," he said. "They could be investigated or treated and suffer the consequences of that treatment without actually benefiting from it."
"Physicians and patients need to be aware of the fact that in prostate cancer, early diagnosis doesn't always mean you're going to get a better benefit."
The task force guidelines, published in Monday's edition of the Canadian Medical Association Journal, apply only to using PSA testing to see if a man might have prostate cancer, not for checking whether treatment is working in men already diagnosed with the disease.
The advocacy group Prostate Cancer Canada was among those that disputed the recommendation, insisting that when performed appropriately, the benefits of PSA screening far outweigh potential harms.
"It's the approach of one size fits all and that doesn't work for health care," said Stuart Edmonds, vice-president of research, health promotion and survivorship at Prostate Cancer Canada.
Edmonds said that based on recently published modelling estimates, doing away with regular PSA screening would double the number of advanced cases — in which the malignancy spreads beyond the prostate gland — resulting in an estimated 13 per cent to 20 per cent jump in prostate cancer deaths each year.
Prostate Cancer Canada suggests PSA testing should be used as part of "smart screening," a personalized approach in which men are tested at age 40 to establish a baseline number; subsequent tests would be performed over time to monitor any changes in that measurement.
"The PSA test, we believe, has an important role in diagnosing prostate cancer early, and that's why we suggest a smart screening approach whereby men get a PSA test and that's added to their risk profile along with their age, their ethnicity and their family history," he said.
"And then that determines when the next PSA test takes place. It could be two years, it could be 10 years. ... We really believe the benefits of the PSA test far outweigh the risk of not doing it."
Dr. Rodney Breau, a spokesman for the Canadian Urological Association, said the new advice is concerning to prostate specialists who believe a lot of good has arisen from PSA screening over the last couple of decades.
In the past, about 20 per cent of men diagnosed with prostate cancer already had metastasis to other parts of the body, reducing the options for successful treatment, said Breau, a uro-oncologist at the Ottawa Hospital. "That's a very rare presentation nowadays, thankfully."
"And the reason for that is PSA screening, there's no doubt about it."
Since PSA testing was first introduced in the early 1990s, the death rate from prostate cancer has dropped by about 40 per cent in Canada, which Breau also attributes to regular screening. (Bell of the task force said there also may be other reasons, including improved treatments.)
"There's no doubt that it has helped many men," said Breau, though he agreed there are also harms that can arise from PSA screening.
"We want to keep the benefits of screening, but we want to reduce the harms," he said, noting that doctors are more judicious about performing biopsies and treating only those men who are likely to benefit.
"There's risks and benefits associated with (screening), but there are ways of mitigating many of those risks."
The conflicting stances on PSA screening will likely lead to confusion, with some men wondering if they should or shouldn't get testing, agreed Edmonds of Prostate Cancer Canada, whose bigger concern is that many men might be less likely to see their family doctor about prostate health in general.
"There's also other aspects to prostate health, with prostatitis and benign prostatic hyperplasia also indicated by a high PSA level," he said.
While Bell said task force members are recommending against routine PSA screening, they understand that some men will want the test anyway.
"Men who are concerned about prostate screening should have a discussion with their physician ... to come up with the decision that's appropriate for that person," he said.
An estimated 23,600 Canadian men will be diagnosed this year with prostate cancer, the most common cancer among Canadian men and the third leading cause of death from cancer, according to the Canadian Cancer Society, and about 4,000 Canadian men will die from the disease in 2014.
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