Who should consider genetic testing for cancer?

Is there a significant history of colon cancer in your family? Was a relative diagnosed with colon cancer at a young age? If so, you may want to talk with your doctor about genetic counseling.

Like all cancers, genetics can play a critical role in how colorectal cancer — which includes cancer of the colon and rectum — develops and progresses. About 5% to 10% of all colorectal cancers are caused by gene mutations inherited through generations.

Genetic counselors help patients and family members understand the likelihood of carrying an inherited mutation, options for genetic testing, genetic tests that may be useful to find a mutation, and what the test results mean. This is true for patients already diagnosed with colorectal cancer and for people with a family history of the disease.

“Knowledge often helps people feel empowered,” says Meera Clytone, MS, a licensed certified cancer genetic counselor with Sharp. "But genetic counselors can also help patients and their loved ones navigate feelings of anxiety."

Types of inherited syndromes

A gene is a segment of DNA that contains instructions for cells to make proteins, which have varying jobs within a cell. Many of these proteins are involved in the response to — and repair of — DNA damage. Others help control how a cell grows and divides.

A gene mutation changes these instructions, affecting a cell’s ability to make proteins. Without these proteins, it becomes more difficult for a cell to correct DNA damage or control how the cell grows, increasing the likelihood that cancer will occur. Because people get half of their genes from their mother and half from their father, a parent who carries a mutation can pass it to their child.

Several gene mutations related to colorectal cancer have been identified. Lynch syndrome is the most common of these, accounting for 3%of all colon cancers. People with this condition face a very high risk of developing colorectal cancer — up to 61%. It can also be associated with an increased lifetime risk of developing other cancers, including endometrial, ovarian, stomach, kidney, pancreatic, brain or skin cancers. The good news is that there are proactive steps that people with Lynch Syndrome can take to reduce their risk, such as undergoing regular colonoscopies.

Other inherited conditions — including familial adenomatous polyposis (FAP) and MYH-associated polyposis (MAP) — can cause numerous polyps (benign growths) to develop in a person’s colon, usually starting at a young age. If untreated, these conditions usually lead to colorectal cancer, typically before age 40.

Who should seek genetic counseling

According to Clytone, you may want to consider genetic counseling if:

• You were diagnosed with colorectal cancer or endometrial (uterine) cancer in the past, especially if diagnosed before age 50

• At least one close relative (parent, sibling or child) was diagnosed with colorectal cancer or uterine cancer before age 50

• You’ve had numerous colon polyps removed (more than 10), or at least one family member had numerous colon polyps

• Multiple family members have had colorectal cancer, regardless of age

Understanding testing and results

Genetic testing is usually performed on a sample of saliva or blood. A positive result could mean a genetic mutation related to colorectal cancer was detected. With guidance from a genetic counselor and other medical professionals, this information can help you make choices related to preventive and proactive care, lifestyle changes and family planning.

“A negative genetic test result may rule out an inherited mutation, but it could still lead to a helpful discussion about other family-based risks,” says Clytone. “A genetic counselor will review all of these and talk to you about screening recommendations.”

Clytone recommends that you check in with your genetic counselor every few years to see if new testing is recommended, especially because the discovery of new genes and techniques to test genes are always evolving.

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