Prostate test may not save lives
March 19, 2009
A pair of huge studies published yesterday cast doubt on whether a popular prostate cancer test saves lives, but the head of the country's largest prostate cancer support group insists it saved him – and hundreds of other members.
Aaron Bacher of the Toronto Man to Man Prostate Cancer Support Group said he will continue to promote the simple PSA blood test as the best way to catch the cancer at its most treatable stage.
"I have no doubt the PSA test saved my life," he said. "I survived because the cancer was caught early and treated."
Two trials, published online yesterday in the New England Journal of Medicine, show the prostate-specific antigen test does little to reduce a man's risk of dying from the disease. They also suggest large-scale PSA testing may lead to more suffering than would the disease it aims to detect.
Dr. Anthony Miller, a study co-author and associate director for research at the University of Toronto's Dalla Lana School of Public Health, said the studies show the test should be used with caution.
They provide "very strong evidence" that a high proportion of cancers detected by PSA testing never would have harmed the men during their lifetimes, Miller said.
"So the detection of prostate cancer was unnecessary and potentially hazardous, and the complications (from surgery) that many of them have suffered – impotence, incontinence – were all unnecessary," he said.
The test, although at risk of yielding false positives, is not itself harmful, but it can trigger a cascade of debilitating treatments – including invasive surgery, radiation and chemotherapy – in cases where the cancer detected would not be lethal.
Cancer experts have eagerly awaited the results of the two trials, which collectively involved more than 230,000 men in the United States and seven European countries. Up until now, there had been no conclusive evidence whether the PSA did more good than harm.
The studies do not close the debate on the PSA test's long-term benefits, but experts say it provides valuable information on the test's potential risks and benefits.
In January, Ontario expanded its funding for PSA testing to include those ordered by a family physician. Previously the test, which costs between $30 and $50, was covered only when ordered at a hospital and paid for by that hospital's operating budget.
Dr. George Pasut, vice-president of prevention and screening for Cancer Care Ontario, said the two studies reaffirm most Canadian guidelines on PSA testing, which already caution health-care providers not to over-prescribe the test and recommends a well-informed discussion with patients to outline benefits and consequences.
"That is what most guidelines recommend ... And I would say both trials, in their separate ways, really reaffirm that," Pasut said.
Prostate cancer is the most common cancer among Canadian men. Last year, an estimated 24,700 males were diagnosed with the disease and 4,300 died from it.
Cancer experts had long hoped the test, which looks for elevated levels of PSA, a protein produced by the prostate that rises in the presence of cancer, would help prevent men from dying of the disease. The two trials cast doubt on that.
The U.S. survey looked at nearly 77,000 men, about half of whom underwent aggressive PSA screening involving six blood tests a year and four rectal exams. The other half was assigned to the regular care of their own doctors, of which half reported having at least one PSA test by the trial's seventh year.
The study, which is ongoing, found about 20 per cent more cancers were detected among men in the aggressively screened group than in the control group. But having the test did not reduce a man's risk of dying from the disease in the first seven years of follow-up.
The seven-country European trial looked at 162,000 men aged 55-69. That trial found no benefit of screening in the first seven years of follow-up care, but did hint PSA screening may prove slightly beneficial with the passage of more time. At nine years of follow-up, there were 20 per cent fewer deaths from the cancer in the screened group.
Dr. Christine Berg, the report's senior author and head of the U.S. National Cancer Institute group running the U.S. study, said PSA testing is almost certainly causing unnecessary suffering in men who receive treatment for cancers they would very likely never die from."Clearly we want to prevent deaths from advanced prostate cancer," Berg said. "But at the same time we want to minimize men living for 15 or 20 years with incontinence from a (prostate removal) that they didn't need."
Berg said positive PSA tests often provoke overly aggressive responses by physicians. "We need a less knee-jerk response to one isolated PSA level," she said.