“Controversy continues over PSA testing for prostate cancer” |
| Controversy continues over PSA testing for prostate cancer Posted: 17 Feb 2011 05:14 PM PST Controversy continues to dog a test used to assess the walnut-sized prostate glands in millions of Canadian men. Two large international studies released Wednesday indicate the prostate-specific antigen test, or PSA, is so rife with problems that leading Canadian specialists say it should not be used as a widespread screening tool for prostate cancer. "Not only does it not appear to reduce death rates from prostate cancer overall, but there are significant harms associated with prostate cancer testing with PSA," says Heather Logan, senior director of cancer control policy and information at the Canadian Cancer Society. Many men have been left incontinent and impotent after undergoing surgery prompted by PSA test results. Dr. Anthony Miller, a highly respected public health researcher at the University of Toronto and co-author of one of the new studies, agrees. He says the current evidence does not support routine PSA screening in men. The PSA test has been widely used in Canada for years, with close to 30 per cent of men over age 50 tested in 2003, according to the most recent figures available from the Canadian Cancer Society. Advocates have been pushing for even more widespread screening in both the U.S. and Canada. PSA is a protein produced by cells of the prostate gland, which is tucked below men's bladders. The protein is normally found in the blood at low levels, and increased levels may indicate prostate cancer. But they can also indicate infection, irritation, or benign swelling. Complicating things even more, prostate cancer can occur without elevating the PSA level. The studies, published Wednesday in the New England Journal of Medicine, were designed to resolve the long-running debate over whether the test should be used as a screening tool. But the journal editors note in an editorial that the controversy "refuses to die." One study, done in the U.S., concludes PSA screening did not cut the death rate. The other study, done in Europe, says screening reduced cancer deaths by 20 per cent. That sounds like a lot, but it is considered a modest gain since so many men have to be tested and treated to prevent one death. Miller summed up the results in an interview saying PSA screening appears to do more harm than good in men over age 70. And there is "very marginal" evidence of benefit in men over 50 because screening leads to significant levels of overdiagnosis and overtreatment, which creates unnecessary stress, anxiety and, in some cases, incontinence and impotence. The U.S. study followed more than 75,000 men age 55 and older as part of a large and ongoing cancer project. Half the men had annual digital rectal exams, PSA tests, or both. The other half received usual care. In the end it made little difference. The rate of death from prostate cancer "was very low and did not differ significantly" between the two groups of men, followed for about 11 years, Miller and his colleagues report. The second study followed 182,000 men in Europe between age 50 and 74 for close to a decade. Half the men had a PSA test every four years, while the men in the control group were offered no testing. The researchers report the PSA screening did reduce the rate of death from prostate cancer by 20 per cent "but was associated with a high risk of overdiagnosis." They note that 1,410 men need to be screened and 48 men need to be treated to prevent one death from prostate cancer. "All and all it is really not a very effective tool to screen for prostate cancer," says Logan, at the Canadian Cancer Society. Miller says the other important message to get across is that detecting cancer early is not always beneficial. He says it is particularly true for prostate cancer, which is often so slow-growing that it will do no harm if left untreated. In these cases, he says the men would normally die of something else. "What you've done is create a circumstance where you've found a cancer, you've had to treat it, and you have all the potential complications of that treatment — incontinence, impotence, post-operative complications," says Miller. "This is what we call overdiagnosis and it is particularly a problem for prostate cancer." While he is against population-wide PSA testing, Miller is not ready to throw the test away. He says it is of value in monitoring patients with elevated PSA levels. But unless a man insists on having the test, Miller says he would not recommend doctors offer PSA testing as part of routine checkups. The advise from the cancer society is a bit more ambiguous. It continues to recommend that men over 50 discuss the potential risks and benefits of prostate cancer testing with their doctors, says Logan. She says men with a family history or other risk factors for prostate cancer might benefit from the test. Logan says the search continues for a more reliable way to identify aggressive and treatable forms of the cancer. Prostate cancer is the most common cancer diagnosed in Canadian men. In 2008, an estimated 24,700 men will be diagnosed with the disease and 4,300 will die of it. © Copyright (c) Postmedia News This entry passed through the Full-Text RSS service — if this is your content and you're reading it on someone else's site, please read our FAQ page at fivefilters.org/content-only/faq.php |
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