Finding Colon Polyps Early Key
Elliot Morris, M.D.
Cancer of the colon and rectum is the second leading cause of cancer deaths in the country. Almost 150,000 new cases will be diagnosed in 2011, and almost 50,000 people will die from the disease. The average American has a 6 percent chance of developing colorectal cancer during their lifetime. It affects men and women in almost equal numbers. Although the disease may occur at any age, the incidence begins to increase dramatically after age 50, and is further increased in those who have affected close relatives.
Although the prognosis for colorectal cancer has improved over the past 20 years, the best opportunity for decreasing death rates attributable to the disease is to diagnosis it an early stage, before symptoms develop. In the vast majority of cases, colorectal cancer develops from polyps, which are small growths that develop in at least 25-30 percent of people after the age of 50. These polyps generally do not cause symptoms, but may, over a period of years, grow and turn into cancer. If the polyps are removed before symptoms develop, the cancer may be prevented.
Since polyps do not cause symptoms, they can only be found with screening tests. The best test, and the one that has consistently been shown to provide the greatest protection against developing colorectal cancer, is colonoscopy. Use of this test can decrease the cancer rate by up to 85 percent. It involves the insertion of a small, flexible tube into the bowel, and permits removal of most polyps right at the time of the procedure. It is done with sedation, and usually takes about 15-20 minutes to perform. The worst part of the procedure is usually the bowel preparation, which involves cleansing of the bowel prior to the exam to permit good visualization of the bowel wall. The accuracy of the procedure has been shown to be greatest when performed by gastroenterologists, physicians with extensive specialized training in the field. Medicare and most insurance companies now partially or fully cover the costs.
Other screening tests for colorectal cancer are available, although less effective than colonoscopy. Fecal occult blood tests involve testing a stool sample for the presence of blood. However, as only a small number of colon polyps bleed, and as not all bleeding is due to polyps, the test is not very accurate. Flexible sigmoidoscopy is similar to colonoscopy in that it uses a flexible scope to evaluate part of the colon, but it only exams the bottom 30-40 percent of the large intestine, and may miss many lesions. Barium enema is an x-ray test that is done to evaluate the colon for abnormalities. It is done without sedation, is generally uncomfortable, and is not particularly accurate. It also does not permit treatment of any abnormalities which may be found. Both it and sigmoidoscopy are rarely performed nowadays. Virtual CT colonography is another x-ray test used to evaluate the colon. It is more accurate than barium enema, but does not permit any therapeutic intervention, and requires a bowel purge similar to that of a regular colonoscopy. If polyps are seen on this exam, a regular colonoscopy, requiring yet another bowel preparation, is required in order to remove the polyps.
Elliot Morris, M.D., is a gastroenterologist in Missoula and is the medical director of the Endoscopy Unit at Community Medical Center.