DNA key to breast cancer in spotlight

Even celebrities are mortal. They share our genes and, like us, cannot escape their inheritance. Angelina Jolie's dignified account of her encounter with her own mortality shines a light on the developing science of genetic diagnosis and DNA profiling, increasingly allowing patients at high risk of inherited diseases to be identified so they can take preventive action.

The BRCA1 and BRCA2 genes were the first to be identified in breast and ovarian cancer more than 20 years ago. Faulty versions of the genes increase the risk of disease at least 50 per cent, the exact proportion depending on other factors. Just as the risk varies from woman to woman, so does the response.

In Jolie's case, it was radical surgery to remove her breasts. But for other women the decisions required may be less radical and distressing, involving modifying lifestyle, having regular mammograms or MRI scans or a course of preventive drugs.

Only in January, Britain's National Institute for Clinical Excellence recommended for the first time that women at high risk of breast cancer be prescribed Tamoxifen or a related drug as a preventive measure. Tamoxifen has been established as a treatment for the disease for decades.

Genetic testing is becoming more common. Testing for specific mutations is already available for a range of cancers, including womb, bowel, stomach and bladder where an inherited faulty gene may increase the risk by 10 per cent to 60 per cent.

The next stage is genetic profiling which offers personal risk analysis, predicting a person's chance of developing disease and enabling treatments to be tailored.

An early example was Greg Lucier, chief executive of Life Technologies, the Californian company that makes machines for reading the human genome, who became a guinea pig for the technology he promotes.

His genetic profile revealed several surprises, including a mutation linked with breast cancer, which could be important to his teenage daughter. He also carried a mutation linked with Parkinson's disease, which his mother had.

But while the threat of breast cancer can be treated with screening, drugs or surgery, there is no staving off Parkinson's, highlighting one of the drawbacks of genetic testing. Is it helpful to know you're at high risk of a terminal disease about which you can do nothing?