Two more genes that could raise risk of breast cancer in women have been identified.
The finding, published today in Nature Genetics, involved more than 80 research institutions collaborating with the Breast Cancer Association Consortium (BCAC) and cancer patients from 16 countries, including Australia.
It appears in the journal with another study, led by Australian-born cancer expert Professor David Hunter, of the Harvard School of Public Health, that also identifies new gene variants that predispose to breast cancer.
These studies flow from earlier UK research from 2007, in which the genomes of 390 women with breast cancer were mapped and compared with the genomes of healthy women.
Using this comparison, the researchers looked for genetic regions that cropped up more regularly in the cancer patients than the control group.
The team then used sophisticated screening technology in a larger cohort of about 80,000 women to isolate the "faults."
Professor Georgia Chenevix-Trench, of the Queensland Institute of Medical Research, says in the latest BCAC study, 800 "possible cancer associations" were initially tested.
This was done over two stages involving 37,012 cancer cases and 40,069 healthy people as controls from 33 studies worldwide.
Professor Chenevix-Trench says the new variants they have uncovered play only a weak role in altering cancer risk.
But the knowledge will in the long-term help identify women who are at greater risk of developing breast cancer, she told ABC News.
"The findings have no impact on treatment, but as more of these weak links are revealed they could play a major role," she said.
"There might be a time when you can have a genetic test to see if you have one, 10 or 100 of these faulty genes.
"But [right now] it does help us understand the biology of the disease and this may lead to better treatment."
Regardless of their role in breast cancer, the findings may have side benefits for cancer research in general, says Associate Professor Jennifer Byrne, at the University of Sydney's Faculty of Medicine.
Genes involved in breast cancer predisposition can also play roles in cancers such as ovarian and prostate, she says.
"They [the variants] may predispose to more than breast cancer in the end," she said.