Women who inherit a damaged version of a particular gene are more than twice as likely to develop breast cancer, according to research published today.
Scientists at the Institute of Cancer Research have quantified for the first time the risk of developing breast cancer for women who carry damaged ATM genes - a genetic fault that affects 0.5% to 1% of the population.
They found that women who carried the damaged gene increase their risk of breast cancer by the time they are 70 from one in 12 to around one in six.
The risk is thought to be greater for women in families with multiple cases of the disease. For women in these families, the findings are likely to mean they will be routinely screened for the faulty gene in the future. Those carrying it will be able to consider whether to have preventative mastectomies to prevent the disease.
The researchers, who were part-funded by Cancer Research UK and whose research is published in the journal Nature Genetics, compared 433 breast cancer patients with a family history of the disease but with no faults in the breast cancer genes BRCA1 or BRAC2, with 521 healthy women. They found 12 ATM gene faults in the breast cancer patients, compared with two in the healthy group, showing a link between the gene and the disease.
The team then conducted a detailed statistical analysis of the data to quantify the risk for women carrying the faulty gene, and found that women in this category had a 2.37 fold increased risk. The findings are seen by cancer experts as of particular interest because relatively little is known about the links between faulty genes and cancer - other than the BRAC genes - which account for 2-5% of all breast cancers and are the only genes which doctors screen for on the NHS.
Between 5-10% of breast cancers are believed to be due to inherited genetic faults - but most of the genes involved in familial breast cancer have not been identified.
For more than 20 years scientists have reported links between breast cancer and the ATM gene but until now there was controversy over the extent of the increase. This study ends that. Nazneen Rahman, professor of cancer genetics at the Institute of Cancer Research, who led the research, said: "Our study provides strong evidence for the first time that damaged ATM genes definitely have a moderate effect on breast cancer risk in a small number of women. Women who carry these genetic faults could benefit from targeted screening."
ATM, like BRCA1 and BRCA2, is a DNA-repair gene, so women with a faulty ATM gene cannot repair damaged DNA correctly. Cells with damaged DNA can begin to replicate uncontrollably and become cancer cells.
