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27 March 2013, 16:00 | Updated: 27 March 2013, 16:08
A study by scientists in Cambridge could see GPs routinely testing patients for their genetic risk of cancer within 5 years.
The biggest investigation of its kind ever carried out has greatly multiplied the number of known genetic markers linked to breast, prostate and ovarian cancer.
In future, the results may make it possible to single out individuals with a potentially lethal hand of genetic cards using a simple saliva test.
They can then be monitored closely for the first signs of developing cancer, or - in the most high risk cases - be offered preventative treatment.
Experts believe the cheap and easy tests could be conducted in family doctors' surgeries.
Samples would initially be sent off to laboratory specialists, but eventually GPs could be doing the analysis themselves.
Study author Professor Doug Easton, a Cancer Research UK scientist from Cambridge University said: "We're on the verge of being able to use our knowledge of these genetic variations to develop tests that could complement breast cancer screening and take us a step closer to having an effective prostate cancer screening programme.''
Ovarian cancer tests are also envisaged, but these will take longer to develop after more research.
The international scientists compared the DNA of more than 100,000 cancer patients with a similarly sized sample from the general population.
They used microchip technology capable of identifying more than 200,000 genetic variants, some of which were suspected of being linked to cancer.
The analysis highlighted more than 80 inherited regions of the genetic code that increase an individual's risk of developing one of the three cancers.
Each variant - a one-letter change in the code called a single nucleotide polymorphism (SNP) - on its own has a small impact on cancer risk. But added together, large numbers of the variants greatly increase the chances of disease.
Professor Ros Eeles, a leading member of the team from the Institute of Cancer Research in London, said: "The SNP test could become widely available for both breast and prostate cancer within five years."
The researchers also stressed that lifestyle and environmental influences worked together with genes to raise the risk of cancer.