British researchers found two previously unreported locations on the genome that are associated with a higher risk of colorectal cancer.

The scientists used a four-phase design, winnowing down more than half a million possible genetic locations to two that were confirmed to correlate with colorectal cancer. In the first phase, they genotyped some 550,000 genetic variants in 940 people with colorectal cancer and 965 healthy people. The people with colorectal cancer also had at least one parent or sibling with the disease, increasing the chances that they would carry a genetic variant. In phase 2, the researchers tested more than 42,000 locations in about 5,600 people.

In phase 3, they tested 11 of the locations that showed the strongest association with disease risk, using about 8,000 people. Finally, they genotyped the two strongest locations in more than 20,000 people from eight centers, confirming the association with colorectal cancer. This study bolsters the theory that genetic risk for colorectal cancer comes from many common genetic variants, each exerting a small influence.

More: To read an abstract of this paper on the medical database PubMed, click here.