Scientists have found the first common genetic trait linked with an increased risk of developing bowel cancer, a discovery that could eventually lead to better diagnosis and treatment of the disease.
Three teams of researchers sifted through the entire human complement of genes to make the find, which they believe will result in a better understanding of why bowel cancer develops in genetically susceptible people.
Each year in the UK some 35,000 people are diagnosed with bowel cancer, which is the third most common cancer after breast and lung, with an annual death rate of 16,100. Around half of the population carry the genetic variant that has now been linked to bowel cancer.
Scientists calculate that carrying the variant increases the risk of developing the disease by about 20 per cent. The lifetime risk of developing bowel cancer is one in 20 for the general population, but this increases to one in 16 for people who have inherited the genetic variant, according to Cancer Research UK, which helped to fund the studies, published in the journal Nature Genetics.
"Each team carried out a whole genome search and pinpointed a gene that is faulty more often among bowel cancer patients than in people without the disease," said a spokeswoman for the charity. "They narrowed down the gene's location within the genome to a region called 8q24.
"Scientists recently found that men who have the same genetic variant are at an increased risk of developing prostate cancer," she added.
Some other genes are already known to contribute to an increased risk of developing bowel cancer, but these are very rare - only about one person in every 2,500 carries any of the known bowel cancer genes.
Both genes and environment - such as diet or lifestyle - contribute to the risk of bowel cancer. Scientists estimated that about a third of bowel cancers have a genetic component, and just 5 per cent of them are linked to previously known genes. The latest studies, however, suggest that the 8q24 genetic variant is linked to about one in 10 bowel cancers diagnosed each year in Britain - about 3,500 cases. Although this is the most important genetic link yet, it is still too small for it to be used as a diagnostic test.
"This is an important first step, but we still have a long way to go before we have a complete picture of all the genes that are involved in inherited bowel cancer risk," said Professor Ian Tomlinson of Cancer Research UK's London Research Institute. "Eventually it may be possible for scientists to design treatments to prevent people at increased risk from developing bowel cancer altogether."