Cells from colon cancer become damaged when their DNA undergoes mutations or changes. Genetic testing can help doctors pinpoint these changes and develop a targeted treatment plan.

Colon cancer involves the growth and spread of damaged cells that originate in the colon. It typically begins as a small growth of cancer cells on the colon’s inner lining. These cells contain genetic mutations that can make them grow out of control.

In most cases, mutations occur spontaneously during an individual’s lifetime. However, up to about 30% of people with colon cancer inherit these mutations. Genetic testing can help determine the type of mutation and inform treatment.

This article reviews how genetic tests for colon cancer work. It also discusses the available tests, who should get them, and how to interpret results.

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People with a family history of colon cancer may have a higher risk of developing the condition. These individuals may choose to undergo genetic testing for colon cancer.

During gene testing, a genetic counselor analyzes a person’s DNA. The counselor looks for mutations in certain genes associated with colon cancer. The genes that they test during this process may include:

  • APC
  • SKT11
  • PTEN
  • TP53
  • MLH1
  • MSH2
  • MSH6
  • PMS2

Mutations in these and other genes can increase the risk of developing colon cancer. In some cases, these genetic mutations pass through families. However, many people with colon cancer acquire these mutations within their lifetime.

Genetic tests can determine whether an individual is at risk for developing colon cancer. They can also identify whether an individual has inherited or acquired certain mutations.

Genetic tests for colon cancer look for genetic mutations that may cause colon cancer. These tests can help identify individuals at risk for colon cancer. They can also help inform treatment for people who already have colon cancer.

FAP syndrome

Familial adenomatous polyposis (FAP) syndrome occurs as a result of mutations in the APC gene. The APC gene is responsible for creating the APC protein. This protein helps regulate cell growth and suppress tumors.

Individuals with faulty APC protein may develop hundreds or thousands of colon polyps. In certain cases, these polyps may become cancerous over time. Genetic tests can identify whether an individual with FAP is at a heightened risk of colon cancer.

Lynch syndrome

Lynch syndrome is the most common type of inherited colon cancer. It involves genetic mutations in the MLH1, MSH2, MSH6, PMS2, and EPCAM genes. Because these genes help cells repair damaged DNA, these mutations can increase the risk of colon cancer.

People with Lynch syndrome typically develop fewer polyps than people with FAP syndrome. However, these growths generally grow and spread more quickly.

MUTYH-associated polyposis

Individuals with MUTYH-associated polyposis (MAP) develop mutations in the MUTYH gene. This gene is responsible for correcting errors in DNA when cells divide.

Most people with MAP develop up to a few hundred colon polyps. Without preventive care, these individuals have an 80–90% risk of developing colon cancer in their lifetime. Genetic testing for MAP can help reduce the risk of developing the condition.

Puetz-Jeghers syndrome

Peutz-Jeghers syndrome (PJS) is a condition characterized by mutations in the STK11 gene. This gene helps suppress tumors. When it becomes damaged, it can increase the risk of colon cancer.

In addition to colon polyps, these individuals may also develop adenomas. These tumors grow in the colon lining and may become cancerous over time.

Certain individuals may be suitable candidates for colon cancer genetic testing. Eligibility criteria for genetic testing include:

  • having a family member with a gene mutation
  • colon cancer diagnosis before age 50
  • having over 10 colon polyps
  • having family members with over 10 colon polyps
  • history of certain other cancers

Researchers have developed guidelines to help doctors identify eligible people. The Amsterdam Criteria recommend genetic testing for colon cancer among individuals who have at least three family members with colon cancer.

These family members should come from at least two generations, and one family member should be a first-degree relative to the other two. At least one of these individuals must have received a colon cancer diagnosis by age 50.

The Bethesda Guidelines also provide recommendations for colon cancer genetic testing. These guidelines require individuals to first meet the Amsterdam Criteria. They then include specific guidance regarding tumor type, age at diagnosis, and more.

Individuals with a personal or family history of colon cancer should speak with a healthcare professional about the possibility of receiving genetic testing.

Genetic testing reveals whether an individual has certain mutations associated with colon cancer. After testing, a genetic counselor will let an individual know whether their test came back positive.

For people who have not had colon cancer, a positive result means that they have a higher risk of developing it. A negative result means that they have not inherited a gene related to colon cancer. However, they may still develop the condition, particularly if it runs in their family.

For people who have already had colon cancer, a positive result means that they may have a higher risk of recurrence. A negative result means that inherited mutations did not cause the cancer. In these cases, they may have acquired a mutation independently.

Individuals with a family history of colon cancer may benefit from genetic testing. This may be particularly true for people who have relatives with identified gene mutations. If colon cancer runs in a family, doctors may also recommend that an individual begin cancer screening at an earlier age.

Anyone concerned about their risk for colon cancer should consult with a healthcare professional. They can provide more guidance about who should undergo colon cancer genetic testing.

Colon cancer is a condition that occurs when cancerous cells in the colon grow and spread. Some people may inherit a genetic mutation that increases the risk of colon cancer.

Genetic testing for colon cancer can help identify which genes contain mutations. This can help doctors predict an individual’s risk of developing this type of cancer. Testing results may also help doctors develop a targeted treatment strategy.

A person can speak with a healthcare professional to learn more about genetic testing for colon cancer. They can offer personalized recommendations for testing.