The federal panel that sets national guidelines for cancer screening is urging Canada's doctors to abandon the PSA test, a simple and widely used blood test that helps catch prostate cancer early but can also lead men to undergo damaging treatments they do not need.
In its first new guidelines on the prostate-specific antigen test in two decades, the Canadian Task Force on Preventive Health Care concluded that the harms of overtreatment outweigh the benefits of early detection, even for men considered at higher risk for prostate cancer.
"Despite 20 years, the amount of evidence that's been brought forward is disappointingly small," said James Dickinson, a professor of family medicine and community health sciences at the University of Calgary and a member of the panel. "The enthusiasts are enthusiastic despite minimal evidence."
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The task force's recommendations, released Monday in the Canadian Medical Association Journal, are sure to reignite the long-smouldering debate about the utility of the PSA test.
The guidelines are already being questioned by groups such as Prostate Cancer Canada and the Canadian Urological Association, both of which favour the PSA test so long as it is used judiciously. They say it is especially useful for men of African descent and men with a family history of prostate cancer, both of whom have a higher likelihood of developing the disease.
"If … PSA testing stops, then what I think is predictable is we'll go back to the era of 30 years ago when most patients presented with advanced disease," said Laurence Klotz, a urologist at Sunnybrook Health Sciences Centre in Toronto. "The mortality will go back up and in 15 or 20 years the task force will reconvene and say, 'Oh, you know something? We blew it.' "
Prostate-specific antigen is a protein produced by the cells of the prostate, a walnut-size gland that is part of the male reproductive system. The test searches for the nanograms of PSA in a millilitre of blood. If the figure is higher than normal, it can be an early sign of prostate cancer.
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There are, however, benign conditions that can boost a man's PSA score, including an inflamed or enlarged prostate. Even if cancer is diagnosed, it can be difficult to predict which tumours will grow and cause symptoms or death, and which would have remained asymptomatic – and harmlessly undiscovered – if not for the PSA test.
In reaching its conclusions, the task force, which was convened by the Public Health Agency of Canada, relied primarily on two large studies, one conducted in the United States, the other in Europe.
The group gave more weight to the European Study of Screening for Prostate Cancer, a randomized control trial that followed more than 162,000 men in seven countries for 13 years.
The European study reported a small absolute reduction in prostate cancer mortality of less than 1 per cent or 13 lives saved per 10,000 men screened. The task force concluded that was too slim a benefit to outweigh the harms that flow from overdiagnosing and overtreating prostate cancers, harms that can range from erectile dysfunction to urination troubles to the side effects of radiation and chemotherapy.
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Dr. Klotz said there have been several developments that the panel ignored, including the trend toward simply monitoring tumours that seem unlikely to grow.
"There's been a complete revolution in this field over, I would say, the last five to eight years, towards what's called active surveillance," Dr. Klotz said. "Patients with the low-grade cancer, which is about half of newly diagnosed cancers, are simply not treated nowadays."
Tony Finelli, a uro-oncologist at the Princess Margaret Cancer Centre in Toronto and chair of the guideline committee for the Canadian Urological Association, said his organization will keep backing the PSA test, despite the task force's advice.
"We continue to believe that a thoughtful discussion between patient and provider is the better way to approach PSA screening and that a widespread recommendation [against PSA testing] would particularly put our at-risk men in a vulnerable position."