Is Colon Cancer Hereditary? Here’s What You Should Know

Colon cancer, also referred to as colorectal cancer, is the third most common type of cancer among Americans. Thanks to cancer research, not only have the treatment options come a long way over the past few decades, we also have a better understanding of the causes.

Mutations in genes lead to cancer. Some of these mutations are caused by exposure to our environment, some are inherited, and other mutations are not yet understood. Only about 5% of all colorectal cancer cases are related to an inherited genetic mutation.

Types of Genetic Mutations that Can Lead to Colorectal Cancer

Let’s take a look at the differences between the various types of genetic mutations associated with colon cancer.

Acquired Gene Mutations: What Are They and How Can They Lead to Colon Cancer?

Most of the time a genetic mutation that leads to colorectal cancer is not inherited, but rather acquired over time. These mutations cannot be passed through your genes to future generations.

• Lifestyle choices - These are things that increase the risk of acquired gene mutations including smoking, obesity, improper diet, sedentary lifestyle, etc.

• Environmental factors - Exposure to smoke, too many sunburns, radon exposure, and chemical exposure can cause genetic mutations. Many people don’t even realize they’ve had exposure to something in the environment that results in a genetic mutation resulting in cancer.

• Uncontrollable factors - There are some risk factors for developing genetic mutations that you can’t control including getting older and your race. African Americans are more likely to develop colorectal cancer than others.

Family Health History and Inherited Gene Mutations

Most patients with colorectal cancer don’t have a family history. But about one-third of patients have at least one other family member who also had colorectal cancer. Genetic mutations that are handed down through the family can be the cause. Keep in mind only about 5% of all colorectal cancers are related to an inherited genetic mutation. And even if a mutation is found, it’s not a sure bet you’ll get cancer. You are, however, at a higher risk.

Because of this, it’s important to know about your immediate family’s health history. This includes your parents, siblings, and children. If your family members were diagnosed under age 50 you’re at an even greater risk of developing this disease as well.

For those with no family history of colorectal cancer, screening is recommended at age 45. But for those with a family history, screening may begin at age 40. The method of screening may also be different from those of average risk who can start with stool samples and move to a colonoscopy in the future. Higher-risk patients may start out with colonoscopies instead.

Hereditary Cancer Syndromes That Increase Risk of Colon Cancer

While an inherited genetic condition is rarely the cause of colon cancer, here are the conditions known to be related to colon cancer and other types of cancer developing in families.

Familial Adenomatous Polyposis (FAP) and Attenuated FAP

FAP is determined when polyps form in the colon or rectum before an individual has reached 20 years of age. Over time, the number of polyps can increase. By the time a person turns 40, polyps can become malignant and lead to a cancer diagnosis. Attenuated FAP is determined when there are less than a hundred polyps in the colon. This is also frequently associated with a delay in the onset of cancer. In these cases, the onset of cancer is normally around the time an individual turns 55 years old.

Both FAP and Attenuated FAP are caused by a mutation located in the APC gene. If your immediate family (parent or sibling) has a mutated APC gene, the potential for developing either condition is characterized as very high.

Lynch Syndrome

Lynch Syndrome is a rare condition but can increase the potential for developing colorectal cancer. Estimates range between a 20-80% likelihood that individuals with Lynch Syndrome will develop colon cancer. This syndrome is also called hereditary non-polyposis colorectal cancer (HNPCC).

A diagnosis of Lynch Syndrome is associated with an increased risk of developing polyps in the rectum or colon. The polyps usually begin as non-cancerous, or benign, but over time they can become cancerous (malignant). In individuals who have Lynch Syndrome, polyps are more likely to become cancerous.

Other rare syndromes associated with inherited colon cancer

• Peutz-Jeghers Syndrome - causing the growth of polyps anywhere in the gastrointestinal tract, including the stomach, colon, or small intestine. Some of the first signs and symptoms of these polyps are pain associated near the affected area, or some bleeding.

• MUTYH-associated Polyposis (MAP) - Caused by a mutation in the MUTYH gene (previously called the MYH gene) this gene is linked to colorectal cancer, but can also cause a variety of other health conditions. Typical cases of MAP result in the development of 10-100 polyps in a specific area, but sometimes more than 1,000 polyps can form.

How to Discover if You Have an Inherited Gene That Could Lead to Colon Cancer

If you have anyone in your immediate family who has been diagnosed with colon cancer, you are at risk. It's important to be aware of the risk factors of colorectal cancer and tell your doctor if this is the case so you can create a screening plan that’s right for you.

Read our blog: When Should You Start Colon & Rectal Cancer Screening.

You and/or the family member who was previously diagnosed with colorectal cancer may want to have some genetic testing done to see if there is a genetic syndrome or mutation other family members may want to know about. If a genetic mutation is found, other family members may want to be tested as well.

A genetic counselor, like those at Affiliated Oncologists, will help you understand if a genetic assessment is right for you and help you through the testing process. In most cases, it’s a blood test that’s relatively painless. The genetic counselor will also help you review and understand the results and what they mean for your cancer risk and your family members’ risk.

If you or a loved one was diagnosed with colorectal cancer, request a consultation with one of our oncologists at a convenient location in the South Chicago suburbs. We can create a customized treatment plan and determine if genetic testing would be helpful for you and your family to understand the future risk for colorectal cancer.

Categories: Colorectal Cancer