Cancers of the colon and rectum start as adenomatous (gland forming) polyps, which develop malignant potential as they enlarge. Only one percent of polyps less than one cm in size have cancer.

In contrast, nearly 30 percent of polyps greater than two cm have invasive cancer and another 30 percent have carcinoma in situ (cancer cells that are only in the inner layer of the colon wall). Finding and removing polyps when they are small largely eliminates the chance of developing colorectal cancer.

Screening recommendations depend on the risk category of the patient. A history of cancer in a primary family member (especially at a young age), inflammatory bowel disease, and genetic syndromes such as Hereditary Non-Polyposis Colon Cancer (HNPCC) or Familial polyposis places a patient at increased cancer risk. A patient with any of these increased risk factors should be followed regularly by a gastroenterologist or colorectal surgeon who can tailor a screening program according to the individual risk.

Patients with bleeding, abdominal pain or bloating, changes in bowel movements, fecal occult blood, iron deficiency anemia or unexplained weight loss are considered symptomatic and should have colonoscopy on an urgent or semi-urgent basis. These symptoms could be a sign of a cancer of the colon or rectum.

Patients over 50 with no intestinal symptoms or increased risk by history have a choice of two screening programs. The well-established program consists of annual stool testing for occult blood combined with flexible sigmoidoscopy every five years. The advantage of this program is simplicity and affordability.

However, it does only directly examine the lower colon and rectum. While half of colorectal cancers and polyps are within reach of the sigmoidoscope, half are not and polyps or tumors in the upper colon may not bleed at the time of testing.

The alternative program calls for colonoscopy every 10 years. While this program is more expensive for each visit, the entire colon and rectum is directly examined.

Patients who have had an adenomatous polyp or a colorectal cancer will need lifelong colonoscopic surveillance. The exact timing of follow up examinations will depend on the location and microscopic appearance of the previous neoplasm.

Life style changes can reduce the risk of developing colorectal cancer. Alcohol and tobacco intake are linked to colorectal cancer as well as other gastrointestinal cancers. Reducing or eliminating alcohol and tobacco exposure will reduce colorectal cancer risk. High fat and low fiber diets are also associated with an increased risk of colorectal cancer. Changing to a high fiber and low fat diet will reduce the risk of cancer. Thirty to forty grams of dietary fiber daily are recommended. Studies have also shown that daily aspirin and folate also reduce the risk of colorectal cancer.

For more information on screening for colon and rectal cancer you can go to Screen for Life: National Colorectal Cancer Action Campaign at www.cdc.gov/cancer/screenforlife or the American Society of Colon and Rectal Surgeons at www.fascrs.org.

(Editor’s Note: Johnny B. Green, MD is the owner of Kitsap ColoRectal Surgery in Bremerton. He is a Fellow of the American College of Surgeons and is Board Certified by the American Board of Colon and Rectal Surgeons. He may be reached at (360) 377-4717.).