How a New Colon Cancer Genetic Test Can Catch More Mutations

Contributor: Brandie Leach, MS, CGC

Genetic testing technology is always evolving. And one newer kind of test — that identifies inherited genetic mutations linked to increased risk for colon cancer — may find genetic changes previously missed by earlier methods.

This newer kind of test, called “next generation sequencing panels,” could result in identifying more people with genetic changes that could predispose them to colorectal cancer — and giving these people the opportunity to take steps to lower their risk.

How genetic testing, counseling is done now

When a patient or family is thought to have a hereditary colorectal cancer syndrome, they currently are referred to a specialist, such as a genetic counselor, for a thorough evaluation of the family history.

Based on the polyps, cancers, and ages of diagnoses in the family members, the genetic counselor may recommend genetic testing for a specific disease. This is because inherited genetic mutations can increase a person’s risk of developing cancer, depending on the function of the gene.

Previously, the most widely used genetic testing method, called Sanger sequencing,  allowed laboratory technicians to read the sequence of a specific gene or a small number of genes. While highly accurate, this method of testing can be costly and labor intensive.

Newer testing methods can give quicker results

Advancements in genetic testing technology now allow for testing multiple genes associated with hereditary colorectal cancer at one time. These tests are called next generation sequencing panels after the technology used to perform the test.

This kind of testing has many benefits, such as the ability to analyze multiple genes at one time, reduced costs, and, in some cases, quicker turnaround time for results.

Perhaps more important, this technology also may find genetic changes, or mutations that were previously missed using Sanger sequencing.

Some limitations

Despite their advantages, the next generation sequencing panels do have some limitations and some caution needs to be taken with them.

Some of these cautions include an increased chance of finding a variant of uncertain significance. This is a genetic change for which we do not have enough evidence to say whether it causes an increased risk of cancer or is just a benign change.

Additionally, many labs that offer next generation sequencing panels might include genes on these panels for which there is limited research. As a result, it is possible we could find a gene mutation, but have limited to no research to guide us on how to best manage a patient to prevent cancer from developing.

Genetic counseling an important part of testing

While initially cautious in the early stages of this testing being used in clinic, we are increasingly using this newer technology to help us to identify more individuals with hereditary colorectal cancer conditions.

As with any genetic testing, we recommend that genetic counseling occur before testing and, when possible, that testing be performed first on someone in the family who has had a related cancer.

Genetic counseling can help people consider the risks, benefits, and limitations of genetic testing in their individual situation.