The colon, or large intestine, is the last few feet of the digestive tract. According to the Cleveland Clinic, colon cancer is the second most common cause of cancer cases and deaths in the United States. With screening tests, doctors can often prevent colon cancer by removing pre-cancerous growths, or catch cancer early enough for a good prognosis.
Purpose
Most people with colon cancer have no obvious symptoms, even when the cancer is fairly advanced. The only way to catch colon cancer at an early stage is with screening tests to detect any abnormal-looking cells in the colon or rectum.
Lesions
Most cases of colon cancer originate in abnormal-looking cells that clump together to form a pre-cancerous growth called a polyp. Polyps often grow on a stalk, in a mushroom-like shape. Other pre-cancerous cells called nonpolypoid lesions are harder to detect because they grow flat on the wall of the colon, but fortunately they are much less common, according to the Mayo Clinic.
Recommendations
The Mayo Clinic discusses recommendations for colon cancer screening. People at high risk of colon cancer, including African-Americans, those with long-standing inflammatory bowel disease or people with a family history of colon cancer, should start screening tests at the age of 45. Others can start screening at age 50.
Tests
There are several tests to screen for colon cancer. The least invasive option is annual testing for small amounts of blood in the stool in a procedure called fecal occult blood testing. Polyp growth can cause slow bleeding into the colon, reflected in microscopic amounts of blood in the stool. Sigmoidoscopy and colonoscopy both involve the insertion of a special tube into the anus and up through the colon to allow the doctor to see any unusual growths. Colonoscopy has the added benefit of allowing immediate removal of any suspicious growths. Virtual colonoscopy using CT scanning also allows a view of the colon, but it might not be as accurate as colonoscopy, according to the Merck Manual, and any suspicious growths will need to be removed in another procedure.
Frequency
Early detection of colon cancer dramatically affects the survival rate, so doctors strongly recommend regular screeding. However, pre-cancerous polyps grow slowly, so aggressive annual screening is not necessary. The Mayo Clinic says that starting at 45 or 50 years of age, depending on their level of risk, people should have annual fecal occult blood testing to screen for colon cancer. In addition, people should have sigmoidoscopy every five years or colonoscopy at least every 10 years.
