Most colorectal cancer does not run in the family. That is why physicians recommend that everyone age 50 and older have periodic colonoscopies. However, when someone does have a relative who has been diagnosed with colorectal cancer, the risk goes up dramatically, and screening guidelines become more stringent.
About 25 percent of colorectal cancer patients can identify a close relative who also has been diagnosed. This could be a first-degree relative — a parent, sibling or child — or a second-degree relative — aunt, uncle, niece nephew, grandparent, grandchild or half-sibling.
Physicians help determine whether a patient has an increased risk of getting hereditary colorectal cancer by asking the following types of questions:
■ Do you have any blood relatives who have had colorectal cancer or precancerous polyps? If so, how many?
The greater the number, the greater the risk.
■ Are those relatives first-degree or second-degree?
The closer the relation, the greater the risk.
■ At what age were they diagnosed with colorectal cancer?
The younger the relative was at diagnosis, the greater the risk.
HEREDITARY SYNDROMES
Patients with hereditary colorectal cancer could be diagnosed with any variety of syndromes. Two of these account for about 4 percent of colorectal cancer cases. Both involve autosomal dominant gene mutations, meaning if just one parent carries the mutation, he or she can pass it on to a child.
■ Familial adenomatous polyposis
This causes thousands of polyps in one individual. Patients with this syndrome will definitely develop colorectal cancer, usually when they are in their 20s or 30s. They also have an increased risk of other forms of cancer, including thyroid, duodenal and gastric. Annual colonoscopies should begin at puberty and continue until the disease progresses to the point where the colon is removed.
■ Lynch syndrome
Patients with this syndrome, which might involve just a single cancerous polyp, have an 80 percent chance of developing colorectal cancer during their lifetime. They also have an increased risk of other forms of cancer, including endometrial, stomach and brain cancer. Colonoscopies should begin around age 20 and be scheduled every two years.
Early colorectal cancer screening can be life-saving for people with one of these hereditary syndromes, since their cancer is likely to develop long before age 50, when most people have their first colonoscopy. A colonoscopy can find evidence of cancer before symptoms arise, and the earlier the diagnosis, the better the outcome. A colonoscopy also can remove polyps before they become cancerous.
GENETIC COUNSELING
People with a family history of colorectal cancer or polyps should talk with their doctor about a referral for genetic counseling.
A trained genetic counselor can review a patient’s family history and determine the likelihood of a family cancer syndrome. The counselor helps the patient decide whether to have genetic testing to confirm the presence or absence of a mutated gene.
Genetic testing does not always provide clear answers, which is why the advice of a genetic counselor is important in deciding on testing and in interpreting the results.
If a mutated gene is confirmed, the patient can improve the likelihood of good health by following early screening guidelines or having surgery. If the mutated gene is absent, the patient is able to follow the lifelong colorectal screening guidelines for people of average risk.
INFORMATION IS KEY
Family members can help save their relatives’ lives by informing the rest of the family about any diagnoses of colorectal cancer or polyps.
Everyone in the family tends to know if a relative is being treated for cancer, since the support of loved ones can help recovery. However, people are less likely to share the news that a routine colonoscopy found and removed precancerous polyps. That information also can help determine the risk of hereditary colon cancer for other members of the family — and possibly save lives.
Dr. Joel Haight is a gastroenterologist with the Penn State Endoscopy Center in State College.
