Colon Cancer by: JoAnn E. Warrick, M.D.
Colon cancer is the 3rd most common cause of cancer, and it is the second leading cause of cancer death in the United States. It affects both men and women equally. It is the most preventable of all types of cancer, and studies show that with regular screening approximately 60% of deaths can be prevented. The reason it is preventable is that it invariably starts as an asymptomatic polyp, and with proper screening and removal, the progression to cancer is halted. Studies also show that there is a 66% reduction in progression to carcinoma in those undergoing a polypectomy.
Although the incidence of colon cancer has been slowly dropping due to increased adherence to screening, there is still a lifetime risk of 4.4% according to SEER data. That means that 1 in 22 Americans will develop colon cancer in their lifetime. The data also shows that approximately 75% of all new cases of cancer occur in those without predisposing factors. Only about 5-10% of all colon cancer is familial. The majority is sporadic meaning no identifiable family history.
Because the risk of colon cancer increases significantly after age 50, all current guidelines recommend screening to begin at age 50 for average risk persons, except in African Americans. The American College of Gastroenterology recommends screening at age 45 in African Americans because they are being diagnosed at a younger average age than other groups. Screening is considered the standard of care and is a part of best practices. Screening is not based on symptoms at all. All asymptomatic persons who are average risk should be offered screening.
There are a variety of methods available for screening. They include an annual fecal occult blood test, periodic flexible sigmoidoscopy, flexible colonoscopy, virtual CT colonography, a specialized stool DNA test (which examines the stool for exfoliated DNA which is a marker for advance polyps and colorectal cancer) and a recently approved serum marker for colorectal cancer.
The non-invasive screening tests typically do not screen for polyps, but instead screen for established colon cancer. Although more invasive, colonoscopy screens for polyps and removes these lesions when detected, and it is also the gold standard. Several studies including the national polyp study suggest that screening colonoscopy reduces the incidence of colon cancer from 76 to 90 percent.
Any of the screening tests mentioned meets the standard of care for screening and the choice of screening should be based on what is appropriate for the patient after an informed discussion of the pros and cons of each of the options. Insurance typically pays for screening colonoscopy, sigmoidoscopy, or fecal occult blood test. The other screening tests are not typically covered by most insurances.