Dr. Michael Hill, Orangeburg surgeon
Colon cancer is the third most common cause of cancer and the third leading cause of cancer deaths in the United States. Risk factors for colon cancer include age, family history of colon polyps, inflammatory bowel disease and hereditary syndromes. Colon polyps are mushroom-shaped abnormal growths that outline the large intestine and protrude into the lumen. Colon cancer typically develops from precancerous polyps in the colon.
Enough is now known about colon polyps that physicians generally place patients in one of four categories: ordinary polyps, hereditary familial polyposis, adenomatous polyps or adenomas and Lynch syndrome.
Most ordinary polyps occur between the ages of 40 and 60. There may be only one or two present, and it may take 10 years or more to become cancerous. There is a hereditary link.
Hereditary familial polyposis is a true hereditary condition in which the entire colon is studded with hundreds, even thousands of polyps. They begin early, even in children under 10 years of age. Virtually every patient with this condition will eventually develop colon cancer. The only known preventive treatment is surgical removal of the colon. Fortunately, this condition is not very common.
Adenomatous polyps or adenomas are growths in the colon that can become cancerous and account for 75 percent of all colon polyps. There are some types of adenoma that differ primarily in the way the cells of the polyps are assembled when they are examined under the microscope. The polyps are referred to as tubular, villous, or tubulo-villous adenomas. Villous adenomas are the most likely to become cancerous, and tubular adenomas are the least likely. Another factor that contributes to the polyp's likelihood of becoming cancerous is size. The larger the polyp, the more likely it is to become cancerous. Once a polyp reaches approximately one inch in size, the risk of cancer is in excess of 20 percent. Therefore, it is advisable to remove polyps of any size to prevent growth.
Lynch syndrome is the disorder that is more common than familiar polyposis but less common than the ordinary polyp. There is a strong tendency of more polyps occurring in close relatives. Polyps and even cancer occur at early ages -- 30s, and sometimes even the 20s. In some families, there is also an increase in breast, ovarian and other types of cancers. A family history of this type warrants very close surveillance of all direct blood relatives.
Most polyps produce no symptoms and often are found incidentally when doing a colonoscopy or x-ray of the colon. Some polyps, however, can produce bleeding mucous discharge, alteration in bowel function or, in rare cases, abdominal pain.
Screening for colorectal cancer increases the chance of survival. There are currently multiple screening options, including fecal occult blood testing, sigmoidoscopy, double-contrast barium enema and colonoscopy. Each of these tests has their advantages and disadvantages.
The initial test performed in most doctors' offices is the fecal occult blood test. The fecal occult blood test finds hidden blood in the stool. The problem with fecal occult blood testing is that it frequently requires multiple samples. The patient's compliance is usually variable because the patient has to handle stool and may find this unpleasant. The test is also limited by diet and medications, which may cause false positive results.
Sigmoidoscopy, double-contrast barium enema and colonoscopy are other screening options. Some patients are resistant to having sigmoidoscopy, double-contrast barium enema or colonoscopy because these tests are usually invasive and require sedation.
Because of those issues, the medical profession has been seeking new ways to screen for colorectal cancer. So far, there is no one best test.
Scientists are working on a test looking for mutated genes in the stool. Stool-based DNA testing is non-invasive. The procedure requires no bowel preparation, and the test has been shown in various trials to be very effective for screening. No direct handling of the stool is required in order to perform the test. A single sample of stool is usually required.
The problem with DNA testing for colorectal cancer is that it costs seven times the amount that is now required for fecal occult blood testing. As a result, it may not be a good, cost-effective screening test at the present time.
Besides the advantages mentioned above, however, I think that people would find DNA testing more feasible in the future once the cost is reduced and it's available to everyone. At some time in the near future, I think this will be the recommended test for colorectal cancer screening.
Orangeburg surgeon Dr. Michael Hill serves as the Regional Medical Center's cancer liaison physician.