Colon cancer is cancer that develops in the colon, or large intestine. This type of cancer is also referred to as colorectal cancer.

According to the American Cancer Society, colon cancer is currently the third leading cause of cancer deaths in the United States. Many factors contribute to the development of colon cancer. Genetics is just one risk factor.

Below, we’ll dive into what percentage of colon cancers are tied to genetics. Then, we’ll examine other risk factors, screening guidelines, and prevention tips.

Colon cancer can definitely run in families. According to the National Cancer Institute (NCI), older research has found that up to 30% of colon cancer diagnoses are associated with familial risk.

The NCI also notes that people with a first degree relative with colon cancer have about double the risk of developing this cancer. People with more than one first degree relative have almost four times the risk.

First degree relatives include:

  • parents
  • siblings
  • children

Familial risk can involve inherited gene changes that increase your risk of colon cancer. Inherited means these changes are passed to you from your parents.

However, in people with a family history of colon cancer, only about 5% to 10% of cases are directly linked with genetic changes. As such, it’s possible that some colon cancers may develop from other genetic changes that aren’t widely tested for yet.

In fact, a 2021 study with 361 people with colon cancer found that 15.5% of them had genetic changes that increased their risk of this cancer. Of these changes, 25% would not have been found using current standards of genetic testing for colon cancer.

Let’s take a closer look at some of the genes known to be involved in an increased risk of colon cancer.


APC encodes a tumor suppressor protein. Normally, tumor suppressors keep cells from growing out of control. When certain changes in tumor suppressor genes happen, this function is inhibited.

When certain genetic changes happen in APC, cells in the colon can grow out of control, causing the formation of hundreds of polyps. This greatly increases the risk of colon cancer.

A few inherited genetic syndromes can increase colon cancer risk and are caused by changes in APC. These are:


Like APC, STK11 also encodes for a tumor suppressor gene. When certain genetic changes happen in this gene, it leads to an inherited genetic syndrome called Peutz-Jeghers syndrome.

People with Peutz-Jeghers syndrome can have more polyps form in the colon, which boosts their risk of colon cancer. They also have an increased risk of several other cancers, such as those of the breast and pancreas.

DNA repair enzymes

A cell must copy its DNA before it divides. Sometimes, errors naturally happen during this process. Proteins called DNA repair enzymes can help detect and fix these errors, preventing changes that could lead to cancer.

Certain changes in genes that encode DNA repair enzymes can also increase colon cancer risk. Inherited genetic syndromes associated with such changes include Lynch syndrome and MUTYH-associated polyposis.

Shared environmental factors

Another factor that can contribute to a familial risk of colon cancer is shared environmental factors. These are experiences or habits shared among family members.

For example, eating a lot of red meat can raise colon cancer risk. Research shows that dietary choices made by parents can influence a child’s dietary choices later on.

So, if you ate a lot of red meat growing up, you may have a tendency to do so as an adult, too.

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At this point in time, we don’t know the exact cause of colon cancer. Overall, cancer happens when cells undergo genetic changes that cause them to grow and divide out of control. It typically takes many of these changes to lead to cancer.

As mentioned earlier, you can inherit some genetic changes from your parents. Additionally, other genetic changes can happen over the course of your lifetime. These are called acquired genetic changes.

While acquired genetic changes can happen due to random errors that occur as cells grow and divide, they may also happen due to medical- or lifestyle-related factors.

Colon cancer risk factors

In addition to genetics, the risk factors specific to colon cancer include:

  • older age, although more younger adults are developing colon cancer now
  • certain racial or ethnic backgrounds, such as being African American or of Ashkenazi Jewish descent, although it’s not fully clear why
  • a history of certain types of polyps or of colon cancer
  • certain medical conditions, like:
    • type 2 diabetes
  • lower levels of physical activity
  • heavy alcohol use
  • smoking
  • a diet high in red and processed meats
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The outlook for people with colon cancer improves when it’s found early. Because of this, regular screening is very important.

The American Cancer Society screening guidelines for colon cancer recommend people with an average risk of the cancer begin regular screenings at age 45 and continue through age 75.

Several testing options can be used for screening. These include both stool- and imaging-based tests, such as:

These guidelines are for people who have an average risk of colon cancer. People who are considered to have a high risk of developing colon cancer may need to begin screening at a younger age or need to be screened more frequently.

It’s important to have a conversation with your doctor about when to start colon cancer screening if any of the following apply:

  • you have a strong family history of colon cancer
  • you’ve received a diagnosis of an inherited genetic syndrome that increases your risk of colon cancer
  • you have a history of certain types of polyps or of colon cancer
  • you’ve received a diagnosis of IBD
  • you’ve had radiation to your abdomen or pelvis as a part of cancer treatment

It’s possible for colon cancer to happen to anyone. However, there are some steps you can take in your daily life to help lower your risk:

  • Get regular screenings: Regular screenings for colon cancer are important for everyone, especially for people with a higher risk. Talk with your doctor about when and how often you should get screened.
  • Adjust your diet: Focus on eating a balanced diet while lowering or avoiding red or processed meats. Additionally, if you drink alcohol, aim to drink in moderation or not at all.
  • Stay active: Physical inactivity increases your colon cancer risk. Try to get regular moderate to vigorous intensity exercise most days of the week.
  • Manage your weight: Overweight and obesity increase colon cancer risk. Talk with your doctor about sustainable ways to manage and maintain a moderate weight.
  • Quit smoking: Smoking increases your risk of colon cancer and many other health conditions. If you smoke, work with your doctor to develop a quit plan.

A family history of colon cancer increases your risk of developing this cancer. In fact, having one close relative with colon cancer can almost double your risk. Both genetic factors and shared environmental factors can contribute to familial colon cancer risk.

But there are steps you can take to manage your risk of colon cancer and improve your outlook if you do develop this cancer.

The outlook for people with colon cancer is best when it’s found early. If you have a family history of this cancer, you may need to begin colon cancer screening early or get screened more often. Make a point of talking with your doctor about when to get screened and how often.