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Genetic test for breast cancer risk factors

30 June 2008
Appeared in BioNews 464

A new, simple genetic test could improve the way breast cancer screening is approached in the UK, according to leading Cancer Research UK scientists. In a report published in the New England Journal of Medicine, the Cambridge University-based research team identified seven new gene variants that are associated with an increased risk of developing breast cancer. They found that by examining which of these variants a woman carries, they could classify the likelihood that she will develop breast cancer as being low, moderate or high. They suggest that this could affect the age at which a woman is encouraged to start having mammograms, and how frequently she subsequently has them.

Breast cancer is the second most common cancer in the UK affecting both men and women, and the risk of developing it is known to be partly influenced by an individual's genetic makeup. Two well-known but rare gene variants in the genes BRCA-1 and BRCA-2 carry, with them between a 36 and 85 per cent chance of developing breast cancer. Screening for these gene variants is currently offered to women with a strong family history of breast cancer. In the new study, the researchers pinpointed seven additional gene variants that are also associated with an increased susceptibility to breast cancer. Importantly, they found that although each of these gene variants individually carries only a mildly increased risk of developing breast cancer, having two or more of these gene variants in combination carries a much greater increased risk.

Currently, NHS mammograms are offered to all women over 50. The researchers propose that testing women for these genetic variants would enable a more targeted approach to breast cancer screening. Dr Paul Pharoah, a member of the Cambridge team explained: 'We believe genetic testing has the potential to enable doctors to identify a woman at an increased risk of breast cancer who would benefit from mammography at an early age... and would also identify a 55-year-old woman with a low chance of breast cancer who possibly wouldn't need such regular checks'.

The genetic test would involve just a simple mouth swab and the technology required is already available. However, the proposal was met with some caution. The researchers estimate that these seven gene variants account for only a third of the genes that influence the risk of developing breast cancer, so the test could not be considered to be comprehensive. Dr Sarah Cant of Breakthrough Breast Cancer commented that the study 'raises interesting questions about how information on risk could be used to help decide who is eligible for screening', adding: 'However, breast cancer risk is affected by lifestyle and environment as well as genetics. These also need to be taken into account when determining risk'.

SOURCES & REFERENCES
Cancer gene test 'for all women'
BBC News Online |  26 June 2008
Gene test gives early alert for breast cancer
The Guardian |  26 June 2008
Genetic test will identify those most at risk of breast cancer
The Independent |  26 June 2008
Polygenic test for breast cancer has utility for screening
PHG Foundation |  26 June 2008
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