Inherited genetic mutations give an 80% chance of breast cancer.© BananastockWomen with defects in one of two genes are highly likely to develop breast cancer, researchers have found. But a healthy lifestyle can reduce this risk.
About 10% of women with breast cancer have mutations in genes called BRCA1 and BRCA2. Those who also have relatives with breast or ovarian cancer have an 80% chance of developing breast cancer, compared with 10% in the general population.
The risk is also close to 80% for women with BRCA mutations but no affected family member, the new study has found1. "The risks are high, full stop," says lead researcher Mary-Claire King of the University of Washington, Seattle.
The finding strengthens the case that all women with a positive genetic test should embark on preventative treatment, such as regular breast screening or even removal of the ovaries.
Screening all women might be worthwhile, adds cancer researcher Ephrat Levy-Lahad of Shaare Zedek Medical Center in Jerusalem, Israel. "This study really supports the idea," she says.
Nature and nurture
Lifestyle is also important, the team found. For example, women born after 1940 with a mutation in one of the two genes have a 67% risk of developing breast cancer by the age of 50. For those born before 1940, the risk is only 24%.
This backs suggestions that modern lifestyles have boosted the risk of breast cancer - although it is not clear why.
“There's a major environmental effect on top of the genetic one”
Ephrat Levy-Lahad
Shaare Zedek Medical
More sedentary lives might play a part. Exercising and staying slim as a teenager tended to delay the age at which women with mutations developed cancer by several years, the study shows. "There's a major environmental effect on top of the genetic one," says Levy-Lahad.
Doctors genetically tested more than 1,000 female New Yorkers with breast cancer, and then tested the families of those with BRCA mutations. The team studied Ashkenazi Jewish women because they carry a handful of mutations that are easy to screen for - but doctors say that the risks are applicable to the general population.
Researchers now hope to track down other genes or factors that predispose women to breast cancer.
Shaare Zedek Medical
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