Genetic Cancer Testing

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Your genes provide a map -- like a basic blueprint -- for your physical body. Your DNA determines blood type, eye color, and even your potential to have an increased risk of the recurrence of cancer. The field of genomics is increasingly prominent in clinical trials and studies, using genetic markers to determine your colon cancer risk and the best treatment option for your type of cancer.

Even as you read this article, genomic science is advancing cancer research in these focus areas:

  • Your susceptibility to colon cancer based on familial gene mutations.
  • The potential for recurrence of colon cancer. 
  • Engineering different types of genetic treatments that can attack mutated DNA.
  • Increasing the reliability of gene testing to monitor cancer growth and reduction using only blood samples.

Can I Skip the PET Scans?

Unfortunately, no. Genomic science has not yet reached this potential. During cancer treatment you will still need screening examinations, such as a PET scan, to determine the status of your cancer. However, we already can use genetic science to detect a potential recurrence of colorectal cancer through blood markers and identify individuals who have the MLH1 or MSH2 genes, which infer an increased risk of recurrence. Hopefully, someday soon we will be able to replace the radiation and radioisotope exposure during routine progress exams with a simple blood test.

Genetic Testing as a Screening Tool

The operative word in this title is tool.

Genetic screening and counseling is not a definitive process -- it's more like a crystal ball that can help your doctor determine what might or might not happen in your future. For example, if you have a strong family history of colon cancer, you may wish to get genetically tested to see if your family carries one of the few inherited conditions that can greatly increase your risk for colon cancer including:

If you know and have proof that your familial risk for colon cancer is higher than average, you will be able to obtain screening exams much earlier than your peers. Likewise, many insurance companies require this proof to cover your screening exams when you get tested early. 

Stool testing for occult blood (fecal occult blood test) has been a prevalent screening tool for colon cancer used for decades. However, with the advent of genomic science, a fairly new way to test stool has emerged as the DNA stool test. It is not widely used, but this test has the potential to identify mutated cells in your stool which are indicative of colon cancer and can be completed in the privacy of your home. Currently, the test still has a fairly high rate of omission, which means that it does not always detect colon cancer.


False Negative and False Positive Results

Both false negative and positive test results do occur in genetic testing and can cause unnecessary stress. Unfortunately, regardless of your test results, there is always a chance that you could still develop colon or another type of cancer. Remember that these are only screening exams to help supplement your medical history and decipher your personal risk for developing colon cancer. Whenever someone seriously considers genetic testing, that person will be sent first to a genetic counselor. These professionals are highly trained to help you understand the pros, cons, and results of your tests. 

Take some time and talk to your doctor and your loved ones. Genetic testing and counseling may not help you at this stage in your life, but it is something to keep mindful of for future options. 


Centers for Disease Control and Prevention. (n.d.). Genetic Testing for Hereditary Colon Cancer. Accessed online May 29, 2014.

National Cancer Institute. (n.d.). Genetics of Colorectal Cancer. Accessed online May 29, 2014.

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