Jun 27, 2019 - Health + Traits

Report Looks at Risk for Hereditary Colorectal Cancer

WS – No Copy

23andMe has added a new Genetic Health Risk report* that looks at two genetic variants in the MUTYH gene (Y179C and G396D) associated with a hereditary colorectal cancer syndrome, MUTYH-associated polyposis (MAP). These two variants are most common and best studied in people of Northern European descent.

Genetics, Environment, and Lifestyle

In January, 23andMe received FDA clearance to offer this information directly to consumers, and our team has been finalizing the report since then.

There are many factors — diet, exercise, alcohol consumption, and smoking, for example — that can influence a person’s risk for colorectal cancer. In fact, most cases are not caused by inherited genetic variants.

However, individuals with two genetic variants or two copies of a genetic variant included in this new report tend to develop colon and rectal polyps, have an increased risk of developing colorectal cancer, and may have a slightly increased risk for certain other cancers.

These two variants account for the majority — from 80 percent to 90 percent — of all MAP variants in people of Northern European descent. Between 1 and 2 percent of people of Northern European descent have one of these variants, which means that between 1 in 10,000 and 1 in 40,000 people of Northern European descent are expected to have MAP.

It’s important to note that more than 100 other variants in the MUTYH gene have been linked to MAP and this report only includes two of those variants. While this report is most relevant for people of Northern European ancestry, the two variants are also found in people of other ethnicities.


“People with MUTYH-associated polyposis (MAP) are at a much higher risk of developing colon and rectal cancers, and it often affects them when they are at younger ages,” said Anjee Davis, President, Fight Colorectal Cancer, a leading colorectal cancer patient advocacy group in the U.S. “However, for people who know that they have MAP, early detection and subsequent screening can be potentially lifesaving. The new 23andMe report is limited in that it only identifies people with MAP — and not other hereditary colorectal cancer syndromes, like Lynch syndrome — but it can be a positive first step for prevention for those who have the two associated variants. Additionally, because only a small percentage of colorectal cancer cases are attributed to a hereditary predisposition, all people need to know the symptoms and be screened at the recommended age.”

Without appropriate surveillance, carrying both of these variants or having two copies of one increases the risk of developing colorectal cancer to between 43 and 100 percent. The risk in the general population is about 4.2 percent.

 Health + Ancestry Service Customers

Eligible 23andMe Health + Ancestry Service customers can view their MAP report. As with other Genetic Health Risk reports considered sensitive, eligible customers must first opt-in to view the report. If they choose to opt in, they will go through a short tutorial detailing vital information to know before seeing their results.

23andMe is committed to ensuring that our customers understand what it may mean to carry a risk variant or variants and what it means not to have one of the variants covered in this report. Specifically, not having one of the variants — or a negative result — does not mean one is not at risk for developing colorectal cancer. Instead, the report highlights the fact that genetics is just one of many risk factors for colorectal cancer.

Family History

More than a hundred genetic variants in the MUTYH gene are linked to MAP, and thousands of variants in other genes are linked to other hereditary colorectal cancer syndromes.

People with two variants or two copies of a variant included in the MAP report have a higher risk for colorectal cancer and the risk for people with one variant is still uncertain. Some studies suggest that people with one variant may have a slightly increased risk, particularly if they have a family history of colorectal cancer. Still, the evidence is limited at this point.

If a person has a positive family history of colorectal cancer or a personal history of colorectal polyps, they should consider talking to a doctor for more screening information. Finally, the MAP report is not diagnostic and is intended for adults only. It is not a substitute for visits to a healthcare professional for recommended screenings or appropriate follow-up. Any result should be confirmed in a clinical setting before taking any medical action.

Learn More

Eligible customers can go to their Health Overview page to view their report. On that page, they will be directed to update their report preferences and choose whether to opt in to receive the report. Not yet a 23andMe customer? Find out more here.

*For important information and limitations regarding each of our genetic health risk reports as well as our other health reports, visit 23andme.com/test-info.

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