Colon Polyps and Cancer

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COLON POLYPS AND CANCER

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Dr. Minocha is a practicing gastroenterologist and author of "Natural Stomach Care: Treating and Preventing Digestive Disorders with Best of Eastern and Western Therapies".

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A polyp is a projection or a "bump" of the bowel wall protruding into the lumen. Polyps may occur anywhere in the gut, but here we will focus only on colon and rectum.

Polyps occur in as many as 40-50% of the population. The number and size of polyps increases with one's age, especially in patients with family history of colon polyps or cancer. High fat, low fiber diet and smoking may play an important role in the causation of these polyps, whereas use of aspirin and similar drugs decrease the risk.

Polyps can be of various sizes, shapes and microscopic structure. Most polyps, when examined under the microscope, demonstrate a benign pathology. However, some of these "benign" polyps can and do go on to become cancer, and are thus precancerous. This type of polyp is known as adenoma. Most colon cancers arise from these precancerous polyps. It takes about 5-10 years for a benign polyp to transform into cancer. While most colon cancers arise from these polyps, most precancerous polyps do not go on to cancer. Polyps of the "hyperplastic" variety are not believed to be precancerous.
As is the case with colon polyps, colon cancer is uncommon before the age of 40, and increases with one's increasing age. While most polyps and early cancers may not cause any symptoms, large polyps may cause some abdominal pain, altered bowel habit or bleeding.
In order to prevent deaths due to colon cancer, it is necessary to detect polyps or early cancers before they cause symptoms. Screening for polyps in average risk subjects over forty years of age without symptoms involves annual testing of the feces for occult blood. When colonoscopy (lower GI scope) is performed in patients testing positive for occult blood, as many as 5-12% are found to have cancer despite being asymptomatic. In addition, precancerous polyps are found among 20-38% of these subjects. Testing the stools for occult blood every year reduces deaths due to colon cancer by 30 percent.
A sigmoidoscopy (scope of rectum and lower colon) is recommended in all average risk subjects after the age of 50 years. Sedatives are generally not used for this procedure. This screening test reduces the risk of dying from colon cancer by as much as 80 percent. If the test is negative, a repeat examination is recommended every five years. On the other hand, if a precancerous polyp is found on sigmoidoscopy, an examination of the entire colon is usually performed to look for coexisting polyps in the rest of the colon.

A colonoscopy is usually performed under sedation. The endoscopist can also remove polyps during this procedure. Such polyps are then examined under a microscope to see if they are precancerous or contain any cancer. Once the colon has been "cleared" of precancerous polyps, a repeat colonoscopy is recommended at 3-5 years. The interval may be shortened in cases where an incomplete first exam was performed or multiple or cancerous polyps are found.

Sigmoidoscopy and colonoscopy are "safe" procedures. However, as is true for most things in life, problems may occur on rare occasions. In addition to the risks of sedation including heart and respiratory problems, the procedures may cause bleeding, or a tear in the colon. In most instances however, the benefits accrued from such procedures outweigh the potential risks.

A barium enema is sometimes used as a screening tool. Patients are not sedated for this test and a scope is not introduced into the colon. Unfortunately, it provides a poor visualization of the lower colon and patients must still undergo a colonoscopy if polyps are detected on barium x ray. Given its limitations, most digestive disease specialists prefer the scope exam over the barium enema.

First degree relatives of patients with colon cancer have an increased risk of precancerous polyps and cancer. The risk is not significant if only one elderly relative is involved. On the other hand, the risk is considerable if there are two or more involved persons in the immediate family, or the family member developed cancer or precancerous polyps before the age of 60 years. The screening program for such patients is initiated at 40 years of age.

Other populations at high risk for colon cancer include those with a family history of familial polyposis, inflammatory bowel disease (ulcerative colitis and Crohn's disease), and hereditary nonpolyposis colorectal cancer. The timing, interval, and type of screening program is individualized based on the diagnosis.

Remember, colon cancer, when detected early enough can be cured. A shining example of such a cure is former President Reagan, who was operated on for colon cancer while he was still in office. If the cancer is detected in late stages, our ability to affect survival is limited. Most insurance programs including Medicare cover most of the screening procedures. I strongly urge you to talk to your doctor about the screening program that would be appropriate for you.

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