Comparing the Benefits and Costs of Testing for Genetic Causes of Colon Cancer FREE

Gene defects contribute in some way to cancer. Most often, cancer develops when several gene defects interact with each other and with exposure to environmental factors, such as cigarette smoke, over many years. Less often, a single defect can be harmful by itself and cause cancer earlier—a good example of this is the Lynch syndrome, a genetic defect that substantially increases the chance that a person will develop cancer, usually of the large intestine (colon) but also at other sites, at earlier ages. It is important to identify the syndrome early so people can decide what to do to prevent the cancer.

To see whether it is cost-effective to test people with colon cancer for the gene defect that causes the Lynch syndrome, and then to identify close relatives at high risk for cancer.

The researchers did not study real people. They used information from studies of real people to develop a computer model of what would happen if people with colon cancer and their close relatives had different tests.

The researchers assumed that everyone with colon cancer would have questionnaires or tests on the colon cancer and then gene tests if needed, or would have all gene tests for the Lynch syndrome up front. Then, healthy close relatives of those who tested positive would also be evaluated and undergo testing for gene defects. The researchers assumed that some but not all healthy close relatives who tested positive for the defect would carefully follow recommendations for screening or would have surgery to remove their colon or uterus and ovaries before cancer developed.

Testing people with colon cancer to identify families with the Lynch syndrome, and then testing relatives who could get treatments to prevent cancer, was cost-effective. Benefits exceeded costs especially for younger people, who could live longer healthy lives by preventing cancer earlier, and for women because of their additional risk for uterine and ovarian cancer.

The study assumed that about one half of close relatives of people with cancer and a gene defect would want to undergo testing for that defect. If fewer relatives choose to have testing, fewer cases of cancer would be prevented and testing would become less cost-effective.

Testing everyone with colon cancer to identify families with the Lynch syndrome seems to prevent many cancers in those relatives at very high risk for cancer at an acceptable cost. However, the findings hold true only if many close relatives of all people with colon cancer and the Lynch syndrome have gene testing, and if healthy relatives with the gene defect undergo intensive cancer screening and possibly surgery to prevent cancer. The genetic testing is not something most doctors and clinics currently do, but testing for colon cancer could be done as a first step in many hospitals and laboratories. Genetic testing could then be done at specialty clinics or by genetic counselors.