When Colorectal Cancer Runs in Your Family

Why you should consider genetic testing

Father and son talking over coffee at a cafe

Just like freckles, curly hair and green eyes, you can inherit colorectal cancer from your parents. It’s important to know if it runs in your family because inherited colorectal cancers:

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  • Occur at a young age.
  • Grow faster.
  • Are associated with other cancers.

“Depending on the particular syndrome you have, you also may be at high risk for cancer in other organs, such as your stomach, bladder, skin, brain, uterus or liver,” says James Church, MD, a colorectal surgeon and expert in inherited colorectal cancer.

Only about 5 percent of colorectal cancers are inherited. They’re rare. But if someone in your family has one — particularly a parent or sibling — you have a higher chance of getting it too.

Are you and your family at risk? Here’s how to know and what to do about it.

How to know if colorectal cancer is inherited

The first clue that colorectal cancer could be inherited is when a younger person gets it.

“Whenever we see someone under age 50 with colon or rectal cancer, we refer them for genetic testing,” says Dr. Church.

The next clue is a history of colorectal cancer in the family. Having a parent, sibling or child with the disease increases your own lifetime risk from about 5 to 15 percent. If the relative with cancer is younger than age 50, your risk is even higher. And if you have more than one first-degree relative with colon or rectal cancer, your risk rises even more.

“A strong family history of colorectal cancer, or even precancerous polyps, may also be an indication for genetic testing,” says Dr. Church.

Ask your family doctor if you are concerned.

Why genetic testing is important

Advances in technology have changed genetic testing dramatically. It’s now much more affordable and readily available.

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With genetic panel testing, one test sequences all the genes that might cause inherited colorectal cancer. If a mutation is detected, all of the person’s at-risk relatives should have genetic testing too.

The goal of testing is to identify those who carry a cancer-associated mutation. These are the people who need to take more aggressive steps to prevent cancer, which includes frequent cancer screenings.

“If there are young children in the family, we may not test them immediately, but rather wait until they reach puberty or young adulthood,” says Dr. Church.

Genetic test results can indicate if you have any of the approximately 10 inherited disorders that can cause colorectal cancer, including:

What to do if a family member has it

If someone in your family has colorectal cancer and a genetic mutation detected on blood or saliva testing, get yourself checked too. Seek a gastrointestinal specialist who is experienced in treating inherited colorectal cancers. It’s not the same as treating regular colorectal cancers, says Dr. Church.

Part of your care should involve talking with a genetic counselor, who can educate you on the disease, its risks and appropriate steps.

Above all, don’t jump to conclusions, says Dr. Church. Just because one of your relations has inherited colorectal cancer, it doesn’t automatically mean you’ll get it as well. (That’s where genetic testing and counseling come in.)

“The affected bloodline has to run through you,” says Dr. Church. “It helps to draw a family tree.”

And even then, not all inherited colorectal cancer syndromes work the same.

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Some, like Lynch syndrome and familial adenomatous polyposis, are dominantly inherited, meaning you need only one parent to pass on the mutated gene to get the disease. These diseases have the strongest family history, sometimes spanning generations. Each child of an affected parent has a 50-50 chance of inheriting the mutation and disease.

Other syndromes are recessively inherited, meaning you need both parents to pass on a mutated gene to get the disease. If you receive only one, you won’t have the disease but will be a “carrier” — and could help pass it along to your child. These inherited colorectal cancers tend not to have a strong family history because most family members who have one mutation don’t have the disease.

“But I prefer not to know”

Some people claim not to want a genetic test so they can’t worry about the results. What you don’t know can’t hurt you, right?

Wrong, says Dr. Church.

“If inherited colorectal cancer runs in your family, you really should talk to a genetic counselor,” he says. “The counselor can explain the advantages of getting tested.”

For example, if the test shows you don’t have the gene mutation, you won’t need to have the screenings — like frequent colonoscopies — required for those who do.

“It’s always good to know your risk because it can help direct your care,” says Dr. Church. “For some, genetic testing and preventive care is the way to survival and a good quality of life.”

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