Over the next five years we might find links to the remainder of all other familial breast cancers

Georgia Chenevix-Trench, research co-ordinator

Since the first two genes were discovered in the mid-1990s, there has been fierce international competition to identify genes that make women susceptible to the disease.

It would appear the Australians, working at the Queensland Institute of Medical Research, have triumphed.

The researchers claim the BRCA3 gene is linked to another rogue gene identified as mutated ataxiatelangiectasia, or ATM, which causes breast cancer.

Georgia Chenevix-Trench, who led the research team, said 60% of women carrying the BRCA3 gene would develop breast cancer before they were 70.

Screening

This is a similar incidence to carriers of BRCA1 and 2.

In an article in the Journal of the National Cancer Institute of the United States, Ms Chevenix Trench said the three rogue genes accounted for about 55% of all hereditary breast cancers.

She said: "About 5% of breast cancers are clearly hereditary.

"Of that 5%, we know about a third of those families affected by multiple cases of breast cancer are caused by gene mutations to BRCA1 and 2.

"My guess is that over the next five years we might find links to the remainder of all other familial breast cancers."

However, experts at Cancer Research UK say they are not convinced by the findings.

Science information officer Sara Hion said: "It's certainly too early to hail this research as being the discovery of BRCA3.

"Cancer Research UK is aware of conflicting data from other groups studying mutations of the ATM gene.

"We await the results of further research with great interest."

The research team believes if doctors can identify people who have the ATM gene fault, they can be targeted for screening and prevention.