Breast Density Linked to Genetic Factors

Breast density, the strongest known risk factor for breast cancer, has been found to be linked to genetic factors, according to a study reported in the September 19, 2002, issue of The New England Journal of Medicine.

The study was conducted by Australian researchers in collaboration with Canadian colleagues. The study involved 607 pairs of twins from Australia and 355 pairs of twins from North America. The researchers found that in both sets, genetically identical twin pairs had similar breast densities. Non-identical pairs of twins, who share half their genes, had breast densities about half as similar. The results show that genetic factors explain why women of the same age have different breast density and explain why having a family history of breast cancer is a risk factor for the disease.

"The hunt is now on to find the genes responsible for breast density,” said Prof. John Hopper, director of the Center for Genetic Epidemiology at the University of Melbourne (Australia; www.unimelb.edu.au). "Once found, the genes may help define new subtypes of breast cancer and enable targeted prevention strategies and treatment.”

Prof. Hopper noted that "there may be many genes involved with breast density, and for an individual woman, it will be the combined effects of these genes rather than a single mutation in just one "high-risk” gene such as BRCA1 or BRCA2.”





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