The program, called "Boadicea," uses detailed family history to predict a woman's risk of developing cancer. It is an improvement over previous programs, researchers say, because it takes into account more genetic mutations.

The researchers plan to offer Boadicea to health professionals to help them pre-select the high-risk women who should have additional genetic testing. Information on the program is available in the British Journal of Cancer.

Women with a strong risk of breast and ovarian cancer can be offered pre-emptive measures -- such as screening from an early age, preventive surgery or chemoprevention.

But the genetic tests needed to identify such high-risk women are expensive, and the results can be slow in coming, causing considerable anxiety in the many patients who turn out not to be at high risk.

"We created the Boadicea program in order to better target genetic testing towards only those women who are most likely to carry the mutations," says Professor Doug Easton of the Cancer Research UK Genetic Epidemiology Unit in Cambridge.

"Boadicea works out a woman's breast and ovarian cancer risk using detailed information on her family history of cancer," Easton explains. "The program calculates both her risk of carrying a particular cancer-causing mutation, and her overall risk of developing breast or ovarian cancer."

Boadicea predicts cancer risk based on detailed genetic data gathered on 1,484 women with breast cancer and 156 families with multiple breast- and ovarian-cancer cases.

The team has just finished testing the program's accuracy by using it to predict high genetic risk of breast cancer in women whose family history was collected in the past by doctors.

Comparing Boadicea's answers to the results of genetic tests in those women has confirmed the program's strength, Cancer Research UK notes.

Many genes are responsible for a woman's inherited risk of breast cancer. Most of these genes have only a small effect on their own, but working together they are a strong influence.

The detailed family data the Boadicea team used in developing the program allows it to take the influence of all of the genes into account -- even those genes for which there is no biological test.

"Having put the finished product through its paces by rigorously testing it, we have confirmed that it is more accurate than any such programme created in the past," Easton says.

The team currently is making Boadicea more user-friendly and plans to make it available via the Internet to oncologists and geneticists.

"[Boadicea] holds the promise to be the most accurate computer-based program available to identify women at high risk of breast and ovarian cancer on account of gene mutations in their families," says Professor Robert Souhami, Director of Policy and Communication at Cancer Research UK.

"Women found to be at high risk of getting cancer can explore opportunities with their doctor to reduce the chances of the cancer developing or to detect it at a very early stage through regular monitoring," Souhami says.