Colon Cancer and Colon Polyps

Cancer of the colon is a significant health problem in the world. It is one of the leading forms of cancer. It is the second most common cancer killer in the USA, causing approximately 55,000 deaths per year. Only lung cancer claims more lives. More than 131,000 cases of colon cancer are diagnosed each year. There is an overall five percent to seven percent chance of developing colon cancer during one’s life. When detected early, colon cancer can be cured in approximately 90% of patients. Most colorectal cancers begin as a precursor lesion - the adenomatous polyp. If polyps are detected and removed, the progression to cancer should be thwarted. Early detection of cancer has been a primary goal, but eliminating cancer thru prevention should be an attainable goal if preventative screening measures are used to find precancerous polyps and remove them before transformation into cancer.

What are Colon Cancer and Polyps?

A polyp is a growth that usually begins on the inner lining of the colon. These fleshy growths can be shaped like a mole or a button or a mushroom and begin very small, but can grow to the size of a golf ball. There are several different types of polyps which are differentiated by their appearance under the microscope. Polyps that are called adenomas are potentially precancerous.

Colon cancer is a malignancy (i.e. not benign) within the colon. A malignancy has the capacity to continue to grow and spread into the tissue around the colon or to other sites within the body, such as lymph nodes, or liver, or lungs. Most colon cancers begin as polyps and as a polyp expands, the growth pattern degenerates into a malignant tumor. This concept highlights a very important issue in colon cancer screening tests. Since most cancers begin as polyps, a principal goal is to find polyps within the colon and remove them prior to their transformation into an actual cancer. Thus, at least theoretically, colon cancer is preventable for many patients who undergo testing for and removal of polyps, if they are found.

Risk Factors for Colon Cancer and Polyps

Familial Polyposis Syndrome, Age, and Diet

The most important identified risk factor to date is genetic. A family history of colon cancer or colon polyps can significantly increase the risk for a patient particularly if a relative developed colon cancer or polyps before 60 years old, or if they have several family members who have had these conditions (colon cancer or polyps). A small percent of colon cancers are due to an identifiable inherited gene which leads to a familial form of polyp syndromes and colon cancer family syndromes. Age is an important risk factor for colon cancer. Both polyps and cancer are rare before 40 years old. Over age 40, the incidence of colon cancer rises progressively. A "Western diet" which is high in fat and low in fiber, is felt to be a minor risk factor. Low content of calcium in the diet may also play a role. An interesting related site on hereditary colon cancer is www.hereditarycc.org

Symptoms of Colon Cancer and Polyps

Most early cancers and polyps produce NO SYMPTOMS. This is why screening examinations are so important! The symptoms that can potentially indicate the presence of cancer or polyp are not specific, they can also be caused by a variety of other problems.

• Blood in or on the stools.

• A change in usual bowel habit such as diarrhea, constipation, difficulty passing bowel movements.

• New onset abdominal pain.

• A change in stool caliber, shape, or form.

Screening for Colon Cancer and Polyps

The first step in screening and preventative techniques involve the willingness on the part of the patient and physician to address these issues and perform appropriate testing. The medical history will provide initial information looking for symptoms that could represent colon cancer or polyps, such as significant change in bowel habits, rectal bleeding, abdominal pain. An examination of the stool to detect microscopic (occult) blood can help to identify cancers and polyps that may be releasing small amounts of blood that is not visible to the naked eye. This is performed by smearing a small amount of stool on the cards which are developed and interpreted in the doctor’s office. Hemoccult cards are a commonly used example of this technique. Since all polyps and cancers do not bleed, however, these tests have limited usefulness and do not guarantee the absence of underlying problems. Hemoccult cards can be negative in nearly half of patients that already have colon cancer!

Small polyp that contained cancer in its tip - later removed with snare technique.

Flexible sigmoidoscopy involves examination of the lower portion (60 cm. or 2 feet) of the colon and rectum with a fiberoptic flexible instrument.

Colonoscopy allows examination of the entire colon with a fiberoptic flexible instrument and is the preferred technique for examination of the colon. It is a thorough, usually safe technique that can detect and remove or biopsy polyps and cancers. It does require a more extensive preparation the day prior to the test and administration of sedatives during the exam to maintain patient comfort (a major positive aspect of the technique to most patients). Additional information about flexible sigmoidoscopy and colonoscopy can be found in separate articles in this web site.

An X-ray of the colon (Barium Enema or lower GI) can be a substitute for patients who are unable or are unwilling to undergo tests discussed above. Polyps and cancers cannot be removed or biopsied with X-ray techniques and there are several areas within the colon that are not well seen and thus lesions may be potentially missed. Medicare does not cover use of barium enema for screening for colon cancer except in few special circumstances.

Virtual colonoscopy use CT or MRI scans to detect lesion. The techniques are still being refined and so far do not find lesions with the same accuracy as colonoscopy. If a lesion is suspected on one of these scans, the patient will still need colonoscopy to confirm it and to biopsy or remove it (patient ends up needing 2 rather than 1 procedures).

Two emerging technologies under development:

1. Stool DNA assays (measures) abnormal DNA material shed into the feces by polyps or cancers. If present, this indicates a probable lesion that should be evaluated with colonoscopy.

2. The Camera Pill is a tiny camera that is swallowed and the GI tract is visualized as the camera passes thru. This technology is very preliminary and not available to the public. So far, it shows the most promise in evaluating the small intestine for rare lesions there.

Guidelines for Screening Tests

The following guidelines are those established by national societies. A screening exam implies an individual is not having any symptoms referable to the colon such as visible blood in the stool, abdominal pain, change in bowel habits.

Screening Recommendations for Average Risk Individuals

Includes persons age 50 and over with no risk factors for colorectal cancer other than age.

• Colonoscopy every 10 years (preferred technique) or

• Annual hemoccult plus Flexible Sigmoidoscopy every 5 years.

Screening Recommendations for Individuals with a Family History of Colon Cancer

One first-degree relative > 60 years old at diagnosis of colon cancer:

• Begin screening at age 40 with colonoscopy q10 years.

One first-degree relative <60 years old at diagnosis of colon cancer or several first-degree relatives with colon cancer or adenomatous polyps:

• Colonoscopy beginning at age 40 or 10 years younger than age at diagnosis of youngest affected relative. Repeat colonoscopy q 3-5 years (mostly q5 years).

Screening Recommendations for Family History Compatible with Hereditary Non-Polyposis Colorectal Cancer Syndrome

This is a genetic syndrome where inherited genes predispose individuals to cancer. The criteria in a family include three relatives with cancers including colorectal, endometrial, pancreatic, ovarian, gastric, small bowel, and kidney. One must be a first-degree relative of the other two. Cancer must span 2 or more generations. At least one case must be diagnosed before age 50.

• Full colonoscopy for all members of the family beginning at age 20-25 every 2 years until age 40 then annually.

• Genetic testing on a blood specimen is available. The HNPCC gene is present in 50% of persons with this syndrome. If the gene is present in family members with cancer, can use genetic testing to screen the rest of the family. 

Screening Recommendations for Family History Compatible with Familial Adenomatous Polyposis (FAP)

This is an inherited syndrome where individuals develop thousands of polyps in the colon and colon cancer 100% of the time.

• Children of persons with FAP should have flexible sigmoidoscopy q1-2 years starting at age 10-12 until age 40, then routine screening.

Genetic testing on a blood specimen is available. The APC gene is present in 80% of persons with FAP. Test index case (youngest case) first. If positive, can use genetic testing in family members with nearly 100% accuracy.

Medicare Coverage for Colon Cancer Screening

• Hemoccult yearly over 50 years old.

• Flexible Sigmoidoscopy every 4 years over 50 years old.

• Colonoscopy every 2 years for high risk individuals (sibling, parent, or child with adenomatous polyps or cancer; personal history of polyp or cancer, inflammatory bowel disease, family cancer syndromes).

• Colonoscopy every 10 years for average risk (this is new legislation passed 1/01 and effective 7/01).

Medicare Alert

Following an extensive lobbying effort by the medical community (our practice was actively involved) Congress enacted a colorectal cancer screening benefit for Medicare beneficiaries effective in 1999. Screening exams are covered including flexible sigmoidoscopy and fecal occult blood testing, and colonoscopy (see above). 

Chemoprevention of Colorectal Cancer

A variety of medications, vitamins, supplements and diets have been and continue to be evaluated as measures to prevent or reduce colon polyps and cancer. Aspirin has been the most widely studied.  Study results show variable success – 30% reduction on some studies and no preventative benefit in others. Based on data available as well as the known risks of aspirin, we can not routinely recommend it for colon cancer prevention. NSAIDs also appear to show a modest protective effect but the risk (mainly of GI bleeding) outweighs the benefit. The newer COX-2 NSAIDs (Celebrex, Vioxx) have less GI toxicity and have been shown in Familial Adenomatous Polyposis to reduce but not eliminate polyps. 

Epidemiologic studies indicate diets high in fruits and veggies and low in fat are associated with lower incidence of colon cancer. These diets are high in folate. Trials of folate supplementation did reduce the risk of colon cancer by 25% after 15 years of use in one study. Studies of fiber have shown little to no benefit of high fiber diets or fiber supplementation in prevention of colon cancer.

Calcium binds bile acids and fatty acids, which may cause hyperproliferation of colonic epithelium. A modest reduction of 15% with supplement has been observed. Antioxidants, Vitamins A, C, D, and E and beta carotene show no protective effect.

Treatment of Colon Polyps and Cancer

The majority of colon polyps are removed at the time of colonoscopy either by removing them with the biopsy forceps to "pinch off" the polyp, or by using a wire snare loop to lasso the polyp where it attaches to the colon wall. An electric current is applied to cut and burn, removing the fleshy polyp for microscopic examination and simultaneously cauterizing the base of the polyp to minimize bleeding. Fortunately, there are no nerve endings within the colon and removing polyps is therefore not painful. These procedures are performed in an outpatient setting.

Colon cancer often requires surgical removal (resection) of the segment of bowel where the tumor is found. During surgery, the surgeon samples lymph node and other areas where appropriate to determine the extent of the tumor (localized within the bowel or spread elsewhere). Further treatment with chemotherapy and/or radiation therapy may then be needed, usually if the tumor has spread through the bowel wall or beyond. If a cancer is found in its earliest stages, while it is only in the tip of a polyp, removal by colonoscopy is sometimes adequate therapy.

Large sigmoid polyp containing cancer. Fortunately, this polyp was able to be completely removed with colonoscopy.

Related Sites

American Gastroenterological Association, http://www.gastro.org

Hereditary Colon Cancer Association, http://www.hereditarycc.org
National Digestive Diseases Information Clearinghouse (NDDIC), http://digestive.niddk.nih.gov

Ohio Society of Gastroenterology Nurses and Associates, http://www.osgna.org