A single blood test for prostate cancer in middle-aged men can predict those at highest risk of dying from the disease, a study has shown.
Researchers have found that 90 per cent of prostate cancer deaths occurred in men with above-average levels of prostate specific antigen (PSA) in their blood at age 60.
The finding, published in the British Medical Journal, casts the controversy over PSA screening in a new light. Although regular screening is widespread in the US, the PSA test is unreliable and has been blamed for causing an epidemic of over-treatment. The problem is that many prostate cancers are slow growing and cause little harm.
But the PSA test cannot distinguish the harmless cancers from the aggressive ones. It is estimated that up to 40 per cent of men aged 70 have prostate cancer but few are aware of it and most will die of something else. The latest study of Swedish men by US researchers suggests that a one-off test at age 60 can identify the half of the male population that is at negligible risk of dying from prostate cancer. Screening could then be concentrated on the other half, which would be likely to improve the benefits and reduce the risks of over-diagnosis and over-treatment.
However, the men who have a greater than negligible probability of developing the disease need not despair. A raised PSA level "is far from being an inevitable harbinger of advanced prostate cancer," the researchers said. Even in those among the top 5 per cent of PSA level reading, only one in six will die of the cancer by the age of 85.
Prostate cancer is the most common cancer in men, with 35,000 new cases a year and 10,000 deaths. It is also one of the most rapidly increasing cancers and there is an urgent need for a reliable test.
In an editorial published with the paper in the BMJ, Gerald Andriole, chief of urologic surgery at Washington University School of Medicine, wrote that young men at high risk of prostate cancer, such as those with a strong family history and high PSA level, should be followed closely, while elderly men and those with a low risk of the disease could be tested less often, if at all.
"Approaches such as these will hopefully make the next 20 years of PSA-based screening better than the first 20," he wrote.
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