What to know about colorectal cancer and genes

By Carol McPhail
cmcphail@health.southalabama.edu

When considering your risk for colorectal cancer, it’s important to know your family history.

“We advise people to consider seeking genetic testing if they have multiple first- and/or second-degree relatives with a history of cancer, particularly if the cancers are rare or early onset,” said Amanda Trulock, M.S., CGC, a board-certified genetic counselor who works with cancer patients at the USA Health Mitchell Cancer Institute. “These could be grandparents, aunts, uncles, cousins, parents, siblings, or even adult children.”

An estimated 5% of all colorectal cancer cases can be linked to Lynch syndrome, the most common form of hereditary colorectal cancer. Lynch syndrome, which also increases the risk for endometrial, stomach, liver, kidney, and brain cancers, is caused by inherited mutations in genes that normally protect people from developing these cancers.

“The error in the DNA sequence means that the gene can’t do its job correctly to protect us from developing cancer,” Trulock said. “It’s as if your genes are playing a sport, and there aren’t enough team members playing defense.”

She points out that people with Ashkenazi Jewish ancestry face an increased risk for Lynch syndrome, as well as other hereditary cancer conditions caused by mutations in the BRCA 1 and 2 genes.

People with a family history of colorectal cancer can make an appointment to see one of the two board-certified genetic counselors at the MCI for genetic testing. Testing involves taking a blood or saliva sample, with results available in three to four weeks. In many cases, health insurance will help cover the cost of the test.

If the results are positive, it doesn’t necessarily mean you will develop cancer, Trulock said. But you might need to begin screening tests and be closely monitored.

With or without genetic testing, the recommendation for when to begin colonoscopy screening is age 45, or five to 10 years prior to the age of the earliest colorectal cancer diagnosis in the family, whichever is sooner. The screening age may be lower if there is a known familial variant in a cancer predisposition gene.

“We know that colon cancer is one of the most detectible types of cancer because of the use of colonoscopy,” she said. “If you know you have a family history, you have the opportunity to get screened and catch it early.”

Other forms of inherited colorectal cancer disorders, collectively referred to as polyposis syndromes, produce multiple polyps in the colon and rectum, increasing the risk of cancer.

Even if there is no family history of colorectal cancer, it’s helpful to know the signs and symptoms and to begin screening by age 45, according to current recommendations. “It’s important to listen to your body if you have any symptoms at all, especially if you have rectal bleeding,” she said.

Other symptoms of colorectal cancer include:

• Abdominal pain and tenderness
• Blood in the stool
• Diarrhea, constipation, or other change in bowel habits that lasts more than a few days
• Weakness and fatigue
• Unintended weight loss