What You Should Know About Colon Cancer

Colon cancer is the second-leading cause of cancer deaths in the U.S., after lung cancer. When recognized early, it is highly curable, but at advanced stages, it is often fatal. Fortunately, you can greatly reduce your chances of dying of this disease by maintaining a healthy lifestyle, getting recommended screenings, and recognizing the early signs of colon cancer.

Risk factors

The primary risk factor for colon cancer is increasing age, starting at about age 50. A diet high in fiber and calcium and low in fat may have a reduced colon cancer risk. Family history or inflammatory bowel disease can move risk to a younger age. But colon cancer can occur in anyone at any age.

Small growths called polyps may occur on the inner surface of the bowel. Some polyps could change into cancer that can obstruct the bowel or invade surrounding tissues. When colon cancer invades lymphatic and blood vessels, tumor cells can travel to lymph nodes around the bowel or to distant organs, such as the liver or lungs, where additional tumors called metastases will grow. This whole process may take many years.

Symptoms

Here are some symptoms that could suggest colon cancer: Any blood in the stool should be discussed with your doctor. As a tumor grows, it may obstruct the bowel, causing crampy pain, diarrhea, constipation or a decrease in the size or shape of the stool. Discuss any significant change in bowel movements with your doctor. With more advanced tumors, symptoms may be less specific, such as weight loss and fatigue.

Screening can save your life

Early colon cancer usually has no symptoms at all. So screening is important for everyone. If pre-cancerous polyps are found, they can be removed easily without surgery. Even if cancer has developed in a polyp, the cancer usually can be removed completely with surgery if found early.

At age 50, you should have already started colon cancer screening. With other risk factors, like family history of colon cancer, screening often starts sooner. Screening should be done before, not after, symptoms are noticed, and should be repeated at intervals.

A standard screening is to test the stool annually for trace amounts of blood (stool giuiac testing). This simply requires placing a small stool sample on a card. A positive test will lead to a detailed colon examination. Since not all polyps and cancers bleed, people relying on stool testing should also have sigmoidoscopy every several years. For this procedure the bowel is cleansed with enemas beforehand and a short flexible scope is inserted into the rectum. This examines about a third of the colon, and any abnormal finds will lead to screening the whole colon.

Many physicians prefer to start with a complete colon evaluation (colonoscopy). For this the bowel must be thoroughly cleansed with a large amount of laxatives beforehand. Any small polyps can be easily removed at the same time, and larger growths can be biopsied to see if they are cancerous. Other options are x-rays, either a barium enema or CT-scanning (virtual colonoscopy). Abnormalities on these x-ray studies require a colonoscopy for further evaluation.

While preparing for screening may be somewhat uncomfortable, the use of sedatives during colonoscopy makes the experience quite tolerable for most people. With normal results, exams need to be repeated only every five to 10 years. Screening can greatly improve your odds against colon cancer.

A diet high in fiber and calcium and low in fat may lower your risk of colon cancer and has many other health benefits. Some drugs such as aspirin and estrogen may reduce the risk of cancer developing, but we don't yet have a standard recommendation for their use. But if you alter your lifestyle and get screened, you can greatly improve your odds against colon cancer.

This article was prepared by Dr. Edward Greeno, medical director, University of Minnesota Physicians, Masonic Cancer Clinic, specialist in gastrointestinal malignancy. 

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