by Michelle Springer, Certified Genetic Counselor

Just in time for Thanksgiving, our friend Michelle Springer sets the stage about genetics, family history and inherited cancer so that if you learn that great aunt Sally had colorectal cancer, you’ll know what to do with that information.

During the holiday season as many of us gather with family, talking about cancer may not be at the top of the list of conversation.

“Please pass the turkey, oh… and does cancer run in our family?”

However, these questions are important to ask and asking during a family gathering may be the perfect place to understand any health conditions that may run in the family. You may be surprised at what new information you’ll learn.

Genetic versus Inherited Cancers

Dr. Dennis Ahnen, one of our MAB members, wrote about Lynch syndrome, one of the genetic syndromes impacting colorectal cancer. Read more.

Many families are touched by cancer, and while all cancer is genetic, only a small percentage of cancer is inherited.

What this means is that all cancer is the result of numerous genetic changes that add up in a cell over time.

Sporadic Cancer

In most cases, the cells in our bodies start out with normal genes and the genetic changes that occur are simply due to our age or environment, as well as other factors. This is referred to as sporadic cancer, which accounts for the vast majority of any given type of cancer.

Most colorectal cancer is sporadic in nature, which does not increase the risk of other family members.

Inherited Cancer

However, approximately 5-10% of all colorectal cancer is inherited.

With inherited cancers, a person actually starts out with one copy of a gene that is not working properly (due to a genetic change or mutation). This mutation essentially leads to a higher risk or predisposition for developing cancer.

Knowing whether or not your cancer is inherited is extremely important.

It can help you understand the underlying cause of your cancer, and it can tell you if you are at risk for developing other types of cancers. Additionally, it can tell you if other family members could also be at risk of developing cancer.

First-degree relatives (parents, siblings, children) typically have a 50% chance of inheriting the same genetic change and risk of developing cancer. Other relatives could be at risk as well.

Determining if Cancer is Inherited vs. Sporadic

David and Kimberly, father and daughter, who have both been diagnosed with colorectal cancer.

Determining if a cancer is inherited is critical because it allows families to do things differently and to be proactive. Many families often refer to this as “knowledge is power.”

Often times, inherited cancer increases your risk of other types of cancer, so you can increase screening and surveillance. Additionally, other family members who are found to carry the same cancer risk will typically start screening at a younger age and will be followed closely with set screening recommendations.

For many families, knowing this information is empowering. They feel they have more control over the cancer that has touched their family.

A Genetic Counselor’s Role

Knowing your family’s health history is especially important in determining if your colorectal cancer could be due to an inherited factor. Individuals who have concern that their cancer (or the cancer in their family) could be inherited can contact a local genetic counselor for further discussion and evaluation.

If you or a close relative has had the following, you may want to consider a cancer risk assessment:

  • Cancer at a young age (under age 50)
  • Multiple primary cancers or bilateral cancer (occurs in both paired organs—e.g., both breasts, kidneys, ovaries)
  • Two or more close relatives with cancer, especially of the same type
  • A relative who is a known carrier of an inherited cancer susceptibility
  • Concern about your family history of cancer

One of the best gifts colorectal cancer survivors can share with friends and family is information about their specific cancer diagnosis to help increase awareness about screening and early detection.

During this holiday season, start the conversation about family health history and bring a whole new meaning to sharing this year.

Tools for talking with your family about colorectal cancer:


Family Genetics Webinar

Genetic Syndromes of CRC Webinar


Family History Worksheet

Family History Tool


If you’ve been impacted by colorectal cancer, we need you! Join us and use your experience, your story and your voice to create real change. Get started by signing up. Next, see all the ways you can do something about this disease and take steps to get connected with our community. Come fight with us.

2 comments on “Genetics and Colorectal Cancer”

  1. 1
    Marina Hewson on December 17, 2015

    Hi. I just started reading your site. My question is both my parents died of colon cancer. Dad had colon liver & Mom had colon anus cancer. My maternal grandparents had some kind of cancer. I’ve had several colonoscopy’s. The last 2 I’ve had polyps, non cancerous. Have I inherited the gene & have I paved it down to my kids? If I don’t get an answer I understand for you are a big organization. Thank you for being there for all the people that need you. Merry Christmas.

    1. 2
      Andrew Wortmann on December 17, 2015

      Hi Marina! Thanks so much for reaching out to us. We recommend talking to your doctor to get the most accurate information for your case.

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