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What is Lynch syndrome, the genetic condition related to colon cancer? | Five Questions

Lynch syndrome is the most common cause of hereditary colon cancer, accounting for between 2% and 4% of all colon cancer cases. And it is associated with colon cancer at a younger age.

Lynch syndrome is the most common cause of hereditary colorectal cancer and uterine cancer.
Lynch syndrome is the most common cause of hereditary colorectal cancer and uterine cancer.Read moreDreamstime / MCT

As colon cancer rates continue to rise among adults under age 55, Penn Medicine researchers are homing in on risk factors that may be putting younger adults at risk for a disease more common among older adults.

About 5% of people who develop colon cancer have a genetic condition that puts them at greater risk.

Lynch syndrome is the most common cause of hereditary colon cancer, accounting for 2% to 4% of all colon cancer cases. And it is associated with colon cancer at a younger age.

Gastroenterologists at Penn Medicine are studying whether a simple genetic test for the condition could reduce rates of colorectal cancer and uterine cancer, to which it is also linked.

Early detection would enable people to reduce their risk of cancer through more frequent screening or catch cancer early.

» READ MORE: Colorectal cancer screening among young adults is increasingly important as cases rise

People of average risk typically begin routine screening through a colonoscopy or stool test at age 45.

To learn more about the condition and the latest research, we spoke with Bryson Katona, a gastroenterologist and director of the Gastrointestinal Cancer Genetics Program and the Gastrointestinal Cancer Risk Evaluation Program at Penn Medicine.

What is Lynch syndrome?

It is the most common cause of hereditary colorectal cancer and uterine cancer. This is a genetic syndrome. Five different genes are affected, and defects in these genes lead to an increased risk of cancer — primarily colorectal and uterine, but also for many other cancers.

Although it varies, depending on the specific gene mutation and the type of cancer, a person’s cancer risk could be increased as much as tenfold.

It’s notable that about one in 270 people — roughly 1.2 million Americans — have Lynch syndrome, which makes it incredibly common. But most people have never heard of it. We think the vast majority of people who have Lynch syndrome have not been tested for it.

Once someone is found to carry Lynch syndrome, the chance of them passing that along to one of their children is 50% per child.

As far as how it causes cancer, the genes involved are ones that serve as the body’s eraser. They help repair errors that occur in DNA. These errors are happening all the time in our bodies. If the genetic machinery has a mutation and is not fixing the errors, it can lead to cancer development.

How is Lynch syndrome diagnosed?

Unfortunately, far too often we don’t diagnose Lynch syndrome until the patient already has cancer. If we knew about it before people developed cancer, we might be able to prevent it.

The syndrome is diagnosed through genetic testing, which has become much easier to do over the last 10 to 15 years. It involves collection of a saliva sample. The test is also getting much more affordable. Insurance often covers it, but if not, the maximum out-of-pocket cost is typically $250.

Who do we test? We would certainly test someone who developed a cancer that could be a Lynch syndrome-related cancer. We would recommend testing for anyone with a family history of Lynch syndrome. We might also test based on an individual’s broader family history — if there are multiple colon cancers or multiple uterine cancers, or if family members have been diagnosed at young ages.

What’s the benefit of early diagnosis?

That knowledge is very powerful. It allows you to take a lot of proactive steps to reduce your long-term cancer risk. One important step is to create a personalized plan for cancer risk management. We take into account the patient’s personal history, the family history and what specific gene mutations the patient has.

Some of the things that can be included in a risk management plan are regular upper endoscopies and colonoscopies. We typically start these tests in the patient’s 20s or 30s. They get repeated every one or two years. That’s quite frequent, but Lynch syndrome cancers tend to develop very quickly, so early detection is important.

For women with Lynch syndrome, because of the concern for uterine cancer and ovarian cancer, it’s typically recommended that they undergo a preventative hysterectomy, usually around age 40. Also, for some women who have higher-risk gene mutations, it’s recommended that their ovaries be removed at the same time.

There aren’t great screening tests for uterine and ovarian cancers, which is the main reason for recommending that these organs be removed prophylactically.

For men with Lynch syndrome, we recommend starting prostate cancer screening earlier than normal — typically around age 40.

Other cancers of concern for those with Lynch syndrome include skin cancer, cancer of the urinary tract, cancer of the small intestine, and pancreatic cancer. The decision to screen for those particular cancers is usually made on an individual basis.

What else can Lynch syndrome patients do to reduce their cancer risk?

Oddly enough, they can take aspirin. Studies show that patients who take aspirin for an extended period of time — several years — may reduce their cancer risk by 50%. So determining whether someone should take aspirin is definitely part of the management discussion and plan.

Patients can also potentially reduce their cancer risk by taking a type of dietary fiber called resistant starch. It’s available as a powder, but it is also in multiple foods, including some types of beans and fruit, especially green, or unripe bananas. A recent study showed that people with Lynch syndrome who took a lot of this resistant starch had a lower risk of upper digestive tract cancers — cancers of the stomach and pancreas.

Are researchers looking at other ways to help patients with Lynch syndrome?

Currently, there is so much research. We are far from any type of therapy that would fix the mutation, since it is present in cells throughout the body. But a lot of work is focused on improving screening for the syndrome and for cancers related to it.

Another important area of research is the development of immunotherapy — finding mechanisms to utilize someone’s own immune system to help attack and fight cancers. This has revolutionized a lot of cancer therapy, and it works particularly well for these Lynch syndrome-related cancers.

Another area of research focuses on how to improve our ability to test relatives. Once we identify a patient who has Lynch syndrome, it’s important to make sure this information gets disseminated to all the relatives so we can determine who is a carrier, and who is not. We would want to test the parents to see if it’s coming from the mom’s side or dad’s side. That way we know which cousins to test. We’d also want to test all the patient’s brothers and sisters, because they would be at 50% risk.

Identifying Lynch syndrome is incredibly important because it allows you to take proactive steps to manage your cancer risk. Knowledge is really powerful in this situation.