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What to Know About Lynch Syndrome

By Kathleen Hall

New data show that 1 out of 279 people in the general population has Lynch syndrome.

The majority of people who develop colorectal cancer don’t have a family history that puts them at increased risk for the fourth most common type of cancer in both men and women. However, 5 to 10 percent of colorectal cancer cases are due to inherited causes.

"Lynch syndrome is one of the most common hereditary cancer syndromes," says Dr. Sapna Syngal, director of research at the Center for Cancer Genetics and Prevention at Dana-Farber Cancer Institute in Boston.

[See: 8 Questions to Ask Your Doctor About Colon Cancer.]

In fact, she says, Lynch syndrome mutations may be as common as BRCA1 and BRCA2, the inherited mutations that raise a woman’s risk for breast and ovarian cancer. Lynch syndrome accounts for about 3 percent of all newly diagnosed cases of colon cancer and 2 percent of endometrial cancers. Syngal says your increased risk for colorectal cancer depends on the underlying genes; some increase your risk as much as 50 to 80 percent.

Lynch syndrome is more common than originally suspected, says Heather Hampel, associate director of the division of human genetics at The Ohio State University Comprehensive Cancer Center. New data show that 1 out of 279 people in the general population has Lynch syndrome. To put this in perspective, the National Cancer Institute estimates that colorectal cancer affects 40 out of every 100,000 people per year in the general population.

People with Lynch syndrome often develop more than one primary type of cancer and tend to be diagnosed with cancer at younger ages. In fact, they have a 70 percent lifetime risk of developing any of the Lynch-associated cancers, including colorectal, endometrial, ovarian, stomach, biliary tract, urinary tract, brain and sebaceous skin cancers. "The risk for endometrial cancer [in women with Lynch syndrome] may be higher than the risk for colon cancer, in some cases," Hampel says.

[See: 10 Seemingly Innocent Symptoms You Shouldn’t Ignore.]

Could You Have Lynch Syndrome?

Just because you have a cancer-predisposing mutation doesn’t mean you’ll automatically develop cancer; it just increases the likelihood you will. Lynch syndrome is caused by a germline mutation (one that’s transmitted to offspring) in one of the DNA mismatch repair genes, which repairs replication-associated errors. If one of your parents has Lynch syndrome, you have a 50 percent chance of inheriting it. Furthermore, even second- and third-degree relatives have an increased risk of inheriting Lynch syndrome. The good news is that if you know you have Lynch syndrome, you can take steps to screen for, and prevent, colorectal cancer. That’s why genetic testing is important.

"If you have colon or uterine (endometrial) cancer and there are other cancers in the family, this could be Lynch syndrome," Syngal says. If you were diagnosed at a young age – before 50 – you should definitely be tested. "We recommend that anyone with colorectal or endometrial cancers test their tumor for mismatch repair deficiency as a screen for Lynch syndrome," she says. You should also undergo genetic testing if you know that someone in your family has Lynch syndrome or your personal or family history of cancer suggests an elevated risk.

Hampel says it’s important to screen for Lynch syndrome among all individuals with colorectal and endometrial cancers and among unaffected individuals with a strong family history of these cancers. Equally important, she says, is to offer testing to all at-risk relatives – beginning with the immediate family, who are all at a 50 percent risk for Lynch syndrome – once a diagnosis of Lynch syndrome occurs.

"We will offer testing to all adult children and siblings as soon as an individual is found to have Lynch syndrome," Hampel says. "In addition, we may test the parents to see which side of the family has Lynch syndrome (if it’s not obvious). This lets us know which aunts, uncles and cousins are potentially at-risk. We test as many at-risk family members as possible to help prevent as many cancers as possible."

What Should You Do if You Have Lynch Syndrome?

Normally, colorectal cancer develops slowly, which is why doctors recommend a 10-year interval for colonoscopies in people at average risk who have a normal screening test. However, colorectal cancer develops rapidly in people with Lynch syndrome, so Syngal says early and frequent screening is important. She recommends people with Lynch syndrome undergo a colonoscopy every one to two years beginning at age 25 (instead of 50 for people at average risk).

Women with Lynch syndrome should also begin screening for endometrial cancer around age 30 or 35 and possibly undergo a preventive hysterectomy once they’re finished having children. Syngal recommends men and women undergo screening for stomach cancer via endoscopy beginning in their early 30s.

Syngal estimates there are about 1 million people in the U.S. who have Lynch syndrome, although the vast majority aren’t aware they have it. "It’s a very under-diagnosed syndrome," she says. Once you know you have it, you can screen for cancers and can prevent many colon cancers by removing polyps during a colonoscopy.

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