DEAR MAYO CLINIC:

My husband turned 50 last week. He's concerned that he is at greater risk for colon cancer. How often should he have a colonoscopy?

ANSWER:

As people get older, the risk of colon cancer goes up. For most people, age 50 is the recommended time to begin regular colon cancer screening, and colonoscopy is one of the recommended screening methods. How often your husband will need a colonoscopy depends on the results of his first exam.

Colon cancer is common. According to the National Cancer Institute, more than 140,000 new cases of colon and rectal cancer are diagnosed in the United States each year. Of those cases, about 93 percent are in people older than 50. In fact, age is one of the most significant risk factors for colon cancer.

But there are other significant risk factors, too. People with a family history of colon cancer --particularly those who have a first-degree relative (a parent or sibling) diagnosed with the disease -- are at a substantially increased risk. Chronic inflammation of the colon that lasts for years, as occurs in Crohn's disease and ulcerative colitis, also raises an individual's chance of developing colon cancer. Finally, a personal history of adenomatous polyps (a specific type of colon polyp) increases the likelihood that colon cancer will develop.

In addition to these significant risk factors, other factors can raise the risk of colon cancer. They include smoking, moderate to heavy alcohol consumption, obesity and an inactive lifestyle.

For people who have no significant colon cancer risk factors other than age, the American Cancer Society recommends that colon cancer screening begin at 50. The purpose of screening is to detect abnormalities such as premalignant polyps or early-stage asymptomatic colon cancers. With regard to screening test options, many medical providers recommend a colonoscopy for their patients. This involves passing a long, flexible tube (colonoscope) into the rectum and advancing it the length of the colon. A tiny video camera at the tip of the tube allows the doctor to view the inside of the entire colon.

There are other colon cancer screening options, as well. One is computerized tomography (CT) colonography (virtual colonoscopy). This exam uses CT imaging to produce a detailed view of the inside of the colon and rectum and doesn't require insertion of a scope into the colon. Another screening option is the fecal occult blood test, a lab test used to check stool samples for blood.

The results of these tests determine how frequently subsequent screening is needed. For example, if no abnormalities are found during a colonoscopy, a follow-up exam may not be necessary for another 10 years. If one or two adenomatous polyps are found, removal of the polyps will be necessary and a follow-up or surveillance examination may be recommended in five years. If multiple polyps are found and successfully removed, the follow-up interval may need to be shortened.

It's very important that your husband begin colon cancer screening now. Colon cancer rarely shows signs or symptoms in its early stages. But when caught and treated early, colon cancer is often curable. In addition, if a screening exam finds colon polyps, removing them can decrease the risk of developing cancer.

Everyone -- but especially people 50 and older -- should watch for possible symptoms of colon cancer. Don't ignore abdominal pain and cramping, a change in bowel habits, or blood in the stool. If you have any of these symptoms, make an appointment to see your doctor.

Mark Larson, M.D., Gastroenterology, Mayo Clinic, Rochester, Minn.

Medical Edge from Mayo Clinic is an educational resource and doesn't replace regular medical care.

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