How Family History Affects Colon Cancer Risk

Just as you inherited your parent’s physical features, you may have inherited their susceptibility for colorectal cancer.

If this type of cancer runs in your family, you've probably heard your parents or other relatives talk about it. You may have learned that family members — either your immediate family (first degree) or your aunts, uncles and cousins (second degree) — have had polyps. Or, you know that certain cancers, such as breast, ovarian and uterine, seem to run in your family.

The fact that certain family members have had some form of cancer means that you may have inherited that risk as well. If possible, find out who in your family was affected, and how. Sharing that medical history with your doctor may go a long way in helping to prevent cancer, determine your screening frequency for it, and decide on the best possible treatment if you do get the disease.

Colorectal cancer specialists have identified high-risk populations to help families decide when screening is needed. Primary characteristics include:

• Patients with one first-degree relative who was diagnosed with colorectal cancer or advanced adenoma (polyps) when younger than age 60
• Patients with two first-degree relatives diagnosed with colorectal cancer or advanced adenoma at any age
• Patients with one first-degree relative diagnosed with colorectal cancer or advanced adenoma at age 60 or older
• Patients with two or more second-degree relatives who were diagnosed with advanced adenoma

In 20 to 30 percent of colorectal cancer cases, a cancer gene begins with the patient, so family history may not be helpful. Some people don't have large families so they don't have a family history to consult. But in 70 to 80 percent of colorectal cancer cases, family history is extremely important.

Experts estimate that between 10 and 15 percent of all familial colorectal cancers developed from an inherited risk. These are the genetic disorders commonly tested in families with a history of colorectal or other cancers. Because these are general descriptions, talk with your doctor about specific characteristics and testing.

Lynch syndrome

One of the most common disorders that occurs in families is Lynch syndrome. It can cause colon cancer to occur in people before age 50 and can be passed on to children.

People with Lynch syndrome — among the most common hereditary cancer syndromes — may need frequent colonoscopies, as often as every one to two years, starting at age 35. It's estimated that as many as one in every 300 individuals may be carriers of an alteration in a gene associated with Lynch syndrome.

Familial adenomatous polyposis

This inherited disorder is known to run in families and may affect as many as half of the members. Patients with familial adenomatous polyposis develop hundreds and even thousands of polyps in the colon. It often is detected in people in their teens and early 20s.

Peutz-Jeghers syndrome

This disorder is characterized by noncancerous polyps that can increase the risk of developing certain types of cancer. People with Peutz-Jeghers syndrome have pigmentation defects that appear as small, dark-colored spots on the mouth, hands and feet.

Ashkenazi Jewish descent

Jewish people who are Ashkenazi, or of eastern European decent, have a higher risk for colorectal cancer than other ethnic groups.

In the past, colorectal cancer specialists looked primarily at the patient and the patient's family history as powerful indicators of colorectal cancer risk. Today, specialists are identifying genes that may increase the risk of the disease in families.

That research is making a difference. Researchers are studying whole panels of genes. When they find a suspicious gene in a patient, the patient's family is tested as well.

If you have the slightest concern that you might have inherited a family gene, get screened. 

Categories: General