Colorectal cancer is the third leading cause of cancer among both men and women in the United States. Regular screening for colon cancer has been shown to greatly reduce the risk of illness and death from this common form of cancer.
The colon is also known as the large intestine and is a muscular tube connecting the small intestine to the rectum. Cancer in the colon results from the rapid growth of abnormal cells, usually in the inner mucous lining of the colon.
In many instances, the development of cancer is preceded by the abnormal growth of non-cancerous cells forming what is known as a “polyp.” A colon polyp is a small nodule on the inner surface of the colon. Certain types of polyps increase the risk for the development of colon cancer.
The risk factors for colon cancer include both family history and environmental factors. The risk of colon cancer is increased for a person whose first-degree relative (parent, sibling, child) has been diagnosed with colon cancer or pre-cancerous polyps (also known as adenomas). The risk is also increased in certain families with so-called “polyposis syndromes.” These are conditions in which family members are known to have developed multiple polyps in the intestines.
Other potential risk factors for colon cancer include smoking, obesity and dietary factors such as consumption of a high-fat, low-fiber diet.
Colon cancer in an early stage and precancerous polyps often produce no symptoms. Therefore, people diagnosed with colon cancer are more likely to present with an advanced case of cancer. However, there are several safe and effective screening techniques for colon cancer. These include fecal blood testing, sigmoidoscopy and colonoscopy.
Fecal stool testing involves the collection of stool on a test card or in a container. This is often accomplished by the patient at home. The specimen is then sent to a laboratory to test for markers of possible cancer. If abnormal, follow-up testing, such as colonoscopy, is often recommended. Fecal stool testing must be performed yearly but is simple to accomplish. There are some limitations to this type of testing. It does not always pick up colon cancer when present and does not allow for the removal of pre-cancerous colon polyps.
Sigmoidoscopy and colonoscopy both involve insertion of a camera through the anus into the large intestine to inspect for polyps or other colon abnormalities. In sigmoidoscopy, the camera is advanced only into the part of the colon nearest the rectum (where most cancers are located). It can occasionally miss cancers or polyps that are farther up in the colon.
Colonoscopy allows for visual inspection of the entire colon using a camera mounted on a tube inserted through the anus. When polyps are discovered, they can be removed for biopsy.
The question often arises about when colon cancer screening should begin. In people with no gastrointestinal symptoms who are otherwise healthy and have no known family history of colon polyps or colon cancer, screening should begin between ages 45 and 50. People with a family history of colon polyps or colon cancer should consult with their doctor about screening, which often is recommended at an earlier age.
Dr. Matthew A. Clark is a board-certified physician in internal medicine and pediatrics practicing at the Ute Mountain Ute Health Center in Towaoc.
