Can a gene test predict breast cancer risk?

A new genetic test could identify women most at risk of breast cancer, according to reports.

A genetic test would mean women could be screened for breast cancer based on their level of risk rather than according to age.

Women could be offered the test in their 30s, up to 20 years earlier than routine screening is currently offered.

Women found to be at high risk could be offered regular scans to detect early malignancy, and would benefit from being able to make appropriate lifestyle changes.

Meanwhile, anyone found to be at low risk could opt out of the routine regular screening offered by the NHS to women over 50, saving the resources used on unnecessary screening, say the papers.

What is the research?
Findings come from an analysis of genetic modelling studies for breast cancer risk by a team from the University of Cambridge.

It focused on seven genetic variants - or single nucleotide polymorphisms - each with a high-risk and a low-risk allele, to identify a woman's chance of developing breast cancer.

These genes are different to the BRCA1 and 2 genes which increase the risk of breast cancer in a small proportion of women. When the seven are considered in combination, they can give a picture of an individual's risk of breast cancer.

The population average lifetime risk of breast cancer is 9.4 per cent. But this goes up to 23 per cent in women carrying two copies of the high-risk allele for each gene. In contrast, women carrying two copies of the low-risk allele for each gene have a lifetime risk of 4.2 per cent.

The researchers recognise that several assumptions need to be overcome. Nevertheless, they reason that stratifying women according to genetic risk would result in targeted screening programmes, which would be more efficient and, as more risk alleles are identified, the efficiency will improve.

Screening targeted to fewer people would mean that more expensive, yet more effective, scans such as MRI could be used rather than mammography, they say.

Genetic screening may be more accurate in identifying those at risk

What do the researchers say?
Lead author Professor Sir Bruce Ponder, director of Cancer Research UK's Cambridge Research Institute, said: 'We think that the difference in risk is sufficient that it should be factored into screening programmes.'

Professor Ponder estimated that it would be about five to 10 years before the health service would be ready to use this kind of genetic test.

'There are a lot more genes to be found. We think about 75 per cent are yet to be found,' he said.

'GPs will be in the front line of explaining to women what this is about.'

What do other experts say?
Dr Sarah Cant, policy manager at Breakthrough Breast Cancer, said: 'It raises interesting questions about how information on risk could be used to help decide who is eligible for screening.

'For GPs right now the main take-home message is that these tests are not available at the moment. GPs should continue to promote breast screening.'

N Engl J Med 2008; 358: 2,796-803

Informing patients

  • Women at high risk of breast cancer could be offered more regular scans to detect early malignancy.
  • A combination of high and low risk alleles determines a woman's risk of developing breast cancer.
  • The population average lifetime risk of breast cancer is 9.4 per cent.
  • GPs should continue to promote breast screening.

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