Screening Procedures for Colon Polyps and Colorectal Cancer

Colon and rectal cancer is the third most common form of cancer in the country, affecting 140,000 people every year. It is responsible for 56,000 deaths annually – the second-most common cause of cancer death in the United States. Fortunately, screening procedures (including colonoscopy) help to prevent colorectal cancer, or to identify it at an earlier, more treatable stage.

Colorectal cancer typically begins in benign, non-cancerous polyps. Finding and removing these polyps will prevent colorectal cancer. If the cancer is found before symptoms develop, it is 90% curable. However, once symptoms (including rectal bleeding, bowel habit changes, abdominal pain, or unexplained weight loss) occur, only 50% of cancers can be cured.

Screening procedures include a barium enema (BE), virtual colonoscopy (CT scan), sigmoidoscopy, or colonoscopy. The BE and CT Scans are x-ray tests which can visualize the entire colon; they do not, however, remove polyps or take biopsies. Flexible sigmoidoscopy examines the rectum and the left half of the colon; colonoscopy examines the entire colon and rectum. Both sigmoidoscopy and colonoscopy can remove polyps or take biopsies; however, if a polyp is found by sigmoidoscopy, a colonoscopy is typically recommended to remove the polyp and to search the remaining colon for other polyps or cancers.

Traditionally, it was believed that most polyps and cancers were in the lower half of the colon, but recent studies indicate that they are equally distributed between the right and left. Furthermore, 50% of advanced polyps and cancers found on the right side of the colon did not have polyps in the lower colon, which would have been detected by sigmoidoscopy (N Engl J Med 2000; 343: 162-68, 169-74). These polyps would have been missed until they grew to an advanced stage and caused symptoms. This is why colonoscopy is the preferred screening procedure.

Maryland State Law (15-837) requires insurance companies to provide colorectal screening coverage in accordance to the latest screening guidelines issued by the American Cancer Society. These 1997 guidelines recommend that an asymptomatic individual 50 years or older with no other risk factors should be screened by:
    1. Annual stool testing for occult blood and a flexible sigmoidoscopy every five years, or
    2. Colonoscopy every 10 years, or
    3 .An air contrast barium enema every five to 10 years.  (www.cancer.org)