Women who carry mutations in genes called BRCA are already known to have a substantially higher risk of breast cancer, at around 65 percent. However, the latest study shows that women who have a BRCA mutation and carry many of the newly discovered gene defects are 80 percent more likely to develop the disease.
In the third part of the project, which involved 130 institutions from around the world, scientists compared the genetic makeup of ovarian cancer patients with healthy women. The study found eight new gene regions that raise the risk of the disease, bringing the known total to 12. Together, these had a marginal effect on cancer risk, raising the lifetime chance of disease from 1.8 percent to about 4 percent.
Eeles said a simple test at a GP surgery could be read by a computer to give each patient a personalized risk profile for the disease. Once the tests are available, doctors could improve their accuracy by adding lifestyle factors into the risk assessment.
For example, the risk of breast cancer is raised by alcohol and a high fat diet, but lowered by childbearing and breastfeeding.
Trials are now under way to work out the best way to use the tests, and how any screening programs might work, or be modified where screening already exists.
In the case of prostate cancer, it is not clear at what age men should be tested to determine their risk of the disease. Since prostate cancer usually only develops after the age of 40, a test much earlier might cause unnecessary and prolonged anxiety. It is not clear either whether men who are found to be at high risk should have blood tests or MRI scans, and when doctors should take biopsies.
Tests for breast cancer risk pose similar problems, though screening procedures, such as mammograms, and interventions, from early use of preventative drugs, to a precautionary operation to remove the breasts, are more established.
The work, led by the Institute of Cancer Research and Cambridge University, was funded by Cancer Research UK and the Wellcome Trust charity, and published as a series of papers in Nature Genetics and several other science journals.
While the studies transform what is known about the genetics underpinning the three cancers, in each case, they account for only 40 percent of the gene faults that must be involved. To discover the rest, which could be many thousands, scientists will need even larger studies, and would involve sequencing a person’s entire genetic makeup.