Scientists are close to identifying which men are at highest risk of contracting prostate cancer after discovering a host of genetic variations that contribute to the disease.
The discoveries, which are published in two studies today, open up the prospect of new tests and treatments for the commonest male malignant disease. The existing blood test is unreliable, often leading to unnecessary, painful and invasive investigations when there is no cancer, or sometimes incorrectly giving men the all-clear when they actually have the disease.
The two studies reveal nine new genetic variations that contribute, when present, to an increased risk of prostate cancer. They take to more than 20 the number of genetic variations associated with the disease, the largest number of genetic risk factors uncovered for any cancer.
Researchers said today's major advances help to explain why the disease runs in families. Ros Eeles, of the Institute of Cancer Research in London, who led the first of the two studies, funded by Cancer Research UK and published in Nature Genetics, said the finding was based on the analysis of the genomes of 38,000 men from 21 studies and confirmed previous research published two years ago.
"These results will help us more accurately calculate the risk that a man could develop prostate cancer which will enable more targeted screening," he said. "Understanding more about these genes could also lead to the development of new treatments."
A quarter of new cancer cases in men are cancer of the prostate. It affects 35,000 a year and causes more than 10,000 deaths. The scientists estimate that 1 per cent of men could be targeted for intensive screening because they will have twice the average one-in-10 risk of developing the disease. The risk for men with a relative who contracted the disease before the age of 60 is four times as great as the average.
The incidence of prostate cancer is increasing rapidly, partly because doctors have begun to look for it and are finding cancer that in the past would have gone undiagnosed.
However, it is different from other cancers because it may not need treatment. This is because in many men it is slow growing and they can live with it without ill effects and die of something else. However, some prostate cancers are aggressive and need aggressive treatment. The most urgent need is for a test that can distinguish the aggressive cancers from the slow-growing ones.
The prostate is a gland at the base of the bladder which produces the semen in which sperm can swim. In one in three men in middle age, the prostate becomes enlarged, causing symptoms such as difficulty in urinating, a weak stream or increased frequency. However, in nine out of 10 cases, the cause of the symptoms is benign.
Genetic screening: A high-risk game
*Genetic profiling – the screening of individuals for genetic variations with links to disease so that they can be targeted with specific treatments – is one of the most exciting developments in medicine. Companies are marketing genetic tests over the internet at prices ranging from £250 to £800, and a genetic screening test for prostate cancer is already available for £250. But critics say it is premature because difficult ethical and practical issues have not been addressed, such as how men at high risk should be counselled and how often they should be tested. Any man identified as at high risk of prostate cancer would face a lifetime of regular tests to check if he was in fact developing the disease, followed by treatment of uncertain effectiveness and with a risk of side-effects.
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