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Colon cancer screening
By Joel L. Colker, M.D.
One of the most common questions that concern people who visit physicians these days is the need for colon cancer screening. Colon cancer is the third most prevalent cancer in the United States and the second most common cause of cancer death. Local and national newspapers seem to carry articles every few months about new methods of detection and prevention, and Katie Couric’s colonoscopy shown on the Good Morning America show in 1998 had almost the same effect on requests for screening as Ronald Reagan’s malignant colonic polyp did in 1985. Fortunately, many studies in the past 30 years permit us to answer these questions about colon cancer screening with some confidence. The basis for our recommendations for screening is the discovery that most colon cancers develop from pre-malignant polyps of the colon. Therefore, if polyps are identified and removed, cancers may be prevented. The screening then both detects cancers that are present and prevents new cancers.
Screening tools
Stool occult blood test. This simple and inexpensive test is available in almost any physician’s office that has been shown to reduce modestly the death rate in groups of people who have been screened compared to those who have not. It is more effective in detecting cancers and large polyps than smaller lesions, and to be most effective, it has to be done annually - a single screen is less effective.
Flexible sigmoidoscopy. This is an examination of the lower part of the colon performed in the doctor’s office after a simple laxative preparation. It takes about five minutes and is safe and relatively comfortable, requiring no pre-medication. Some internists and family physicians do the exam themselves and some send their patients to gastroenterologists or surgeons for it. The cost is modest and is covered by Medicare and most insurance plans for those over age 50 and those with bowel symptoms or other risk factors. For screening, the American Cancer Society suggests an exam every five years. Flexible sigmoidoscopy has also been shown to reduce cancer death rates in screened populations, but its effectiveness is limited to the area seen on exam, which on many occasions is quite limited. This lessens it value considerably, especially in higher risk patients.
Colonoscopy. This is an examination of the entire colon and can include biopsy an/or removal of tumors or polyps found. The exam is performed by trained gastroenterologists or surgeons in specially equipped outpatient units of hospitals or clinics. It requires a more thorough laxative preparation than does sigmoidoscopy and usually includes some pre-medication to ensure a complete and comfortable exam. This is the most complete and accurate method of detection/prevention of colon cancer now available (76%-90% reductions in cancer death rates in screened populations). It is more expensive than sigmoidoscopy, but increasingly covered by insurance. Medicare had in the past covered only high risk patients, but will soon pay for screening of average risk patients as well. For screening purposes, an exam every 10 years is probably adequate, but for those with previous polyps, cancer or colitis, more frequent exams are necessary.
Tests in development. In the next decade we will probably be seeing stool tests for abnormal genes or proteins produced by tumors and genetic testing of people for susceptibility for colon cancer. A type of MRI termed virtual colonoscopy has been developed but it so far hasn’t been suitable for screening.
Recommendations
Since the risk of colon cancer is low until the age of 50, most people can wait until then to start screening.
Those with a family history of colon cancer in close relatives (particularly when the cancer has appeared before age 60), those who have themselves had polyps or cancers found in the past, and those who have had ulcerative colitis of Chrohn’s disease for over 10 years fall into a high risk group and therefore should start screening at a younger age. The same probably applies to those who come from a family in which there is a history of several members with various kinds of cancer, particularly colon, stomach, breast, ovary and brain.
Conclusion
Colon cancer screening offers the promise of a substantial reduction in suffering and death and of a lesser cost to society in dollars spent on treatment of the disease and loss of productive individuals. The main reasons why these techniques have not yet had a greater impact on national cancer mortality have been lack of knowledge of the tests’ value among both paitents and physicians, slowness of insurers to cover the cost of this and other preventive services, and our normal fear and embarrassment in undergoing these exams, Fortunately, the first two factors are being overcome, and resources are being put into place to provide screening for those who need it. There is no reason to put it off for another day.