Colon Cancer Genetic Testing

Colorectal cancer develops in the large intestine. It can occur in both the colon and the rectum (the lowest section of the colon).

The cancer usually begins as polyps — small growths on the colon ‘s inside wall. Your doctor can remove polyps during a routine colonoscopy, an examination of the colon using a flexible video camera or scope.

Because colorectal cancer is often a hereditary disease caused by gene mutations, you may wish to find out about your risk, and whether you should consider genetic testing.

Predisposing Factors of Colorectal Cancer

Look at your family ‘s medical history for clues about your risk for colorectal cancer. If one parent has the disease, you have a 50 percent chance of having the same gene mutation. If both parents have it, your risk increases to 80 percent.

Having the mutated gene does not mean that you will get colorectal cancer. It just means that your risk is higher than the general population.

Risk factors of colorectal cancer include:

  • a family history of colorectal cancer over at least two generations (i.e., a parent and a grandparent with the disease)
  • a family history of contracting cancer before age 50
  • three or more family members who have had colorectal cancer, especially if the list includes a parent or sibling.

Genetic Testing

You may wish to consider genetic testing if colorectal cancer runs in your family. While genetic testing is not a substitute for a proper diagnosis, it can tell you if you ‘ve inherited a mutated gene that could lead to cancer. Screening can help you assess your risk and make decisions regarding screening and prevention.

Your doctor may wish to test an affected family member (someone who has already contracted colorectal cancer) before testing a healthy person. If the affected person is found to have a mutation, then doctors will often agree to genetic testing on other family members.

If a mutation is not found in the affected family member, it means that the genetic cause of the cancer in the family is unknown. In this case, the rest of the family should not be screened. But they should consider themselves at high risk and follow screening and prevention guidelines appropriately.

Methods for Screening Colorectal Cancer

A knowledgeable healthcare provider can arrange genetic testing for you. The test is simple on your end:

  • Your physician draws a small amount of blood from your arm.
  • The blood sample then goes to a testing lab for analysis. Usually, the DNA is retrieved from white blood cells for study. The DNA is isolated, and then tests are performed. If the lab technicians find a positive result, they must repeat the test to confirm it. The analysis is time-consuming, and it may take weeks or months for you to get your results.
  • If a mutation is found in one family member, the rest of the family can be tested for the same mutation. These tests go more quickly because the lab technicians are only searching for one mutation, rather than screening all cancer-related genes for any possible mutation.

Working Toward a Cure for Colorectal Cancer

With early detection, colorectal cancer patients have a high survival rate. Colorectal cancer has a 90 percent permanent recovery rate if it is diagnosed early. This is why genetic testing and colorectal cancer screening are so important.

Methods for colorectal cancer prevention include following a diet low in fat and high in fiber. Some scientists believe that aspirin and calcium also help prevent this type of cancer.


Appel, M. (2007). Information on colon and rectal cancer. Retrieved November 10, 2008, from the St. Luke ‘s Heath System Web site: and Rectal Cancer