Understanding what cancer genes really mean for a person with Lynch syndrome

February 28, 2012 | by City of Hope Staff

When scientists link a gene to a particular kind of cancer, like BRCA and breast tumors, it’s easy to get excited about the discovery’s cancer-fighting potential. But what does it actually mean? Usually, zapping the gene won’t suddenly kill the cancer. But in many situations, discovering a gene’s relationship to cancer can identify people at high risk for the disease so they can take steps to avoid it.

That’s the case with Lynch syndrome, a group of hereditary cancers. It’s caused by inherited defects in specific genes that are supposed to repair small mistakes that can happen when DNA copies itself. Only 2 to 4 percent of all colorectal cancers are due to Lynch syndrome, and there are no treatments that specifically target these cancers.   So, what’s the point of genetic testing for colorectal cancer patients to identify those with Lynch syndrome? City of Hope cancer geneticists say the cancer risk supports it. Writing in the Journal of Clinical Oncology, the researchers note that 70 to 80 percent of those with Lynch syndrome will develop colorectal cancer during their lifetime. About 40 to 60 percent of women with the syndrome will develop endometrial cancer during their lifetime, and risks are increased for gastric, ovarian, urinary tract, liver, small intestine, brain and other cancers, as well.

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Despite the need, there are no established national guidelines for Lynch syndrome testing in colorectal cancer patients, says Deborah MacDonald, Ph.D., R.N., A.P.N.G., an assistant professor in the Division of Clinical Cancer Genetics and senior author of the study.

National Cancer Institute-designated comprehensive cancer centers are leading the way, with 71 percent of centers conducting genetic testing for Lynch syndrome. Only 36 percent of community hospital cancer centers provide genetic testing for it, according to the researchers.

Finding out that someone has Lynch syndrome opens the door for physicians to help the patient’s entire family. That help can be anything from more frequent cancer screenings to changes in diet to lower cancer risk — steps that may save lives.

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