hands holding a digestive system model

Is Colon Cancer Hereditary?


  • Researchers cannot yet definitively answer the question, “Is colon cancer hereditary?”
  • They do know, however, that in 30 percent of cases, colon cancer runs in families.
  • Inheritable genetic mutations can predispose people to colorectal cancer.
  • Lynch syndrome and familial adenomatous polyposis are genetic mutations that can lead to colon cancer.
  • You can prevent colorectal cancer by adopting a healthy lifestyle and screening often.

If you have someone in your family who has colorectal cancer, you are more likely to develop the disease. One in three cases of colon cancer occurs in people with a family history of the disease. This means that while the disease can be hereditary, doctors find most colorectal cancers in people with no family history.

Is Colon Cancer Hereditary?

A family history of colon cancer places you at a higher risk of developing the disease. This does not mean that you will inevitably get colon cancer during your lifetime, nor does it mean that you are safe from the disease if no one in your family has it.

Some people with a family history of colorectal cancer never develop the disease. Conversely, some people without a family history do develop colorectal cancer. Other risk factors, like lifestyle choices and diet, also play a role in your risk for colon cancer.

If a first-degree relative (parent, child, or sibling) has colorectal cancer, your risk of developing the condition increases significantly. If doctors diagnose a first-degree relative with colon cancer before age 50, your risk increases further.

Although they agree that colon cancer is hereditary to some degree, researchers have yet to learn why.

Cancers and other diseases may “run in the family” for several reasons. In addition to genes, families share scores of environmental factors that may lead to medical conditions, such as nutrition, shared playspaces, and environmental stressors. Because of these connections, it’s difficult to determine the exact role genes play in hereditary diseases.

If your family history puts you at risk for colorectal cancer, talk to your doctor and work out how to adapt your prevention methods to your heightened risk profile.

Here are steps you can take to reduce your risk:

  • Start screening for colon cancer early, before the age of 45.
  • Screen for colon cancer more frequently.
  • Get regular colonoscopies as recommended by your healthcare provider.
  • Consider genetic counseling to decide whether you should undergo genetic testing.

When Colon Cancer Runs in Families

Researchers know that around five percent of colon cancer patients inherit genes that lead to conditions that may degenerate into colorectal cancer.

Inherited gene mutations probably account for more than five percent of cases. These are due to obvious gene mutations that doctors know and understand well. The remaining inherited cases likely occur due to single-gene mutations that are more difficult to pinpoint and study.

dna strand

Through genetic testing, doctors can identify the most common syndromes that can lead to colorectal cancer.

The following conditions represent our best understanding of why colon cancer runs in families.

Lynch Syndrome (Hereditary Non-polyposis Colon Cancer)

Lynch syndrome is an inherited genetic condition that entails a defect in one to three specific genes. The defective genes are responsible for repairing damaged DNA. When DNA goes unrepaired, cancer can rear its head.

Patients with Lynch syndrome may develop polyps in their colons, but these polyps tend to be few. The lifetime colorectal cancer risk of a Lynch syndrome patient can be as high as 50 percent, compared with 1.2 to 1.51 percent in the general population.

How much additional risk Lynch syndrome involves depends on which gene it affects. Lynch syndrome sufferers tend to develop colon cancer earlier in life. Given its effects on DNA, the condition can cause many other cancers.

Lynch syndrome can trigger cancers in the:

  • Pancreas
  • Stomach
  • Ovaries
  • Breasts
  • Prostate
  • Small intestine
  • Bile ducts
  • Brain

Researchers have found Lynch syndrome responsible for about three percent of all colon cancer cases.

Familial Adenomatous Polyposis (FAP)

FAP is another genetic irregularity people can inherit from their parents. The condition causes hundreds or even thousands of polyps to develop in the colon. The development of polyps typically starts at the age of 10 to 12. Colorectal cancer can appear around age 20. At 40, most people with FAP have colon cancer.

Although more aggressive than Lynch syndrome, FAP is less common. Researchers attribute about one percent of all colorectal cancer cases to this condition.

Peutz-Jeghers Syndrome (PJS)

Another condition affecting genes, PJS predisposes people to colorectal and other forms of cancer. Those who have this syndrome develop polyps called hamartomas that can turn cancerous easily.

MUTYH-associated Polyposis (MAP)

MAP is highly likely to lead to colon cancer in sufferers. Those struggling with this syndrome develop many polyps in their digestive tracts. These polyps require constant regular surveillance from a young age as they are highly likely to turn cancerous.

This genetic mutation happens on the level of the MUTYH gene, affecting its ability to proofread DNA and fix errors in it.

genetic testing

The Importance of Genetic Testing

Through genetic testing, doctors can identify mutations in patients’ DNA. If testing is positive, they can draw conclusions about the patient’s vulnerability to cancer.

We share our genes with our family members, so if a relative of yours has a genetic anomaly, you are more likely to have the same genetic problem. The role of genetic counseling is to determine who in the family should undergo genetic testing.

Genetic testing can help your doctor:

  • Determine whether you have inherited a genetic condition that may affect your health before you develop any symptoms
  • Pinpoint a genetic condition if you already have symptoms
  • Find out how likely your offspring are to inherit the condition
  • Determine a customized action plan for cancer prevention or treatment

When to Seek Genetic Counseling: Genetic Testing Guidelines for Colon Cancer

Doctors have noticed that families with Lynch syndrome tend to share some characteristics. They have compiled their observations into two sets of guidelines they use to determine whom they should test for genetic problems.

Amsterdam Criteria

According to the Amsterdam criteria, a family may be prone to Lynch syndrome if at least three people in the family had colorectal cancer attributable to Lynch syndrome.

  • Of these three people, one is a first-degree relative of the other two.
  • The three relatives span two successive generations.
  • At least one had cancer before the age of 50.

Doctors see the Amsterdam criteria as a guideline and not exact science.

The Bethesda Guidelines

Doctors use the Bethesda guidelines to determine whether a person with colon cancer should undergo testing for Lynch syndrome. According to these guidelines, patients may have Lynch syndrome if:

  • They had colon cancer before the age of 50.
  • They had cancer linked to Lynch syndrome.
  • They’re older than 50 and younger than 60, and their cancer shows signs indicative of Lynch syndrome under the microscope.
  •  A first-degree relative of the patients also had colorectal cancer before 50.
  • They have two second-degree relatives who had colon cancer, possibly as a result of Lynch syndrome.

If they find genetic mutations indicative of Lynch syndrome, FAP, PJ, or MAP, doctors may recommend that the entire family of the patient be tested.

How to Reduce Your Risk for Colorectal Cancer

You can’t control your genetic makeup and predisposition for colorectal cancer. But you can control your lifestyle, habits, diet, and environment. Don’t smoke, drink, or eat fatty foods. Get regular exercise.

If you have a family history of colon cancer, it’s important that you get regular screening. You can now do colorectal screening from home with an at-home colorectal screening test.

eDrugstore Can Help

We carry mail-in kits that are convenient and non-invasive, requiring only a stool sample from you. Our colon cancer screening kits deliver your results in two to five days.

If your results are positive, our U.S.-licensed doctors can recommend further testing and advise you on how to proceed from there.

With any type of cancer, early detection saves lives, particularly if you’re at high risk. Take charge of your health and order your test kit today.

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