New test for hereditary bowel cancer

UK scientists have developed a new genetic test to identify bowel cancer patients who have an inherited form of the disease. The team, based at Edinburgh University, says that the test could also be used to detect people at high risk of developing the disease, before any symptoms appear. The findings, published in the New England Journal of Medicine, suggest that around four per cent of bowel cancer patients have hereditary nonpolyposis colon cancer (HNPCC) - a higher figure than previous estimates.

Most cases of colon cancer are not inherited, but a small proportion of patients have HNPCC, also known as Lynch syndrome. This hereditary form of the disease is caused by a mutation in one of several 'mismatch-repair' genes, which make proteins that fix genetic mistakes incurred when cells divide and multiply. The decreased ability of patients with HNPCC to repair such genetic errors increases the likelihood that a particular cell will acquire mutations that make it cancerous. As well as colon cancer, people who inherit HNPCC are at increased risk of womb and other cancers.

In the latest research, the scientists looked for mutations in the mismatch repair genes MLH1, MSH2 and MSH6. It is thought that mutations in these three genes together account for the vast majority of HNPCC cases, although other genes are also involved. They studied 870 patients under the age of 55 - regardless of family history - who had been newly diagnosed with colorectal cancer. The team found that 38 of the patients had inherited a gene mutation in one of the three mismatch repair genes. The study also found that twice as many men carried a gene mutation as women, and that having a mutation had no effect on the patients' survival.

Team leader Malcolm Dunlop said that 'the study has allowed us to develop a new means to identify patient groups who are likely to carry genetic defects responsible for their bowel cancer'. Using the results, the researchers have developed an online resource for clinicians, to assess which patients need a genetic test. Professor Dunlop said that in the long term, this approach could be used to offer tests to the relatives of these patients, before they develop the disease. Professor Alex Markham, chief executive of Cancer Research UK, welcomed the study. 'These are very valuable findings that will help scientists better understand the process of bowel cancer development, particularly in people who are diagnosed at a young age', he told BBC News Online.