A team of international researchers have discovered an additional 72 common genetic variants that put women at higher risk of breast cancer.
The findings from the world's biggest genetic study of breast cancer, published in journals Nature and Nature Genetics, bring the number of known genetic markers for the disease to about 180.
Professor Georgia Chenevix-Trench - head of the Cancer Genetics Laboratory at the Queensland Institute of Medical Research (QIMR) - says they now have a greater understanding of the inherited causes of breast cancer.
She hopes this will lead to improved screening and prevention strategies for at-risk women in the future.
"Many women are offered mammogram screening when they are middle-aged, but if we know a woman has genetic markers that place her at higher risk of breast cancer, we can recommend more intensive screening at a younger age," said Prof Chenevix-Trench.
The large study involved more than 550 researchers from about 300 institutions in six continents, including Australia's QIMR, University of Melbourne and Cancer Council Victoria.
In total they analysed genetic data from 275,000 women, with and without breast cancer, from across the globe.
As a result they found 65 genetic variants that predispose women to overall risk of breast cancer.
"These are all common variants, so we all carry them and each one of them seems to be associated with a relatively small increase in risk," said co-author Associate Professor Roger Milne at Cancer Council Victoria.
The more of these variants a woman carries, the greater their risk of developing breast cancer, says Ass Prof Milne.
A further seven genetic variants were discovered that predispose women specifically to oestrogen-receptor negative breast cancer, which often leads to poorer health outcomes because it does not respond to hormone therapy.
This aggressive form of breast cancer is less common - affecting about 20 to 30 per cent of all breast cancer patients - but little has been known about its causes, says Ass Prof Milne.
"A better understanding of the biological basis of oestrogen-receptor negative breast cancer could lead to more effective preventative interventions and treatments," he said.