Colon Cancer Screening and Polyps

Cancer of the colon is a major health problem in the United States.  It ranks as a leading form of cancer, along with lung and breast cancer.  Importantly, colon cancer is also one of the most preventable and curable forms of cancer.  When detected early, more than 90 percent of patients can be cured.

This disease begins in the cells that line the colon.  There now is strong medical evidence that there are abnormal genes for colon polyps and cancer that can be passed from parent to child.  The genes within each cell are the hereditary structures that tell the cell what it should do.  When these controlling genes are absent there is a tendency to grow polyps.  The cells in the polyp eventually become uncontrolled and turn into a cancer.  Colon cancer also can develop with other conditions, such as ulcerative colitis, a chronic inflammation in the colon.

What is a Colon Polyp?

A polyp is a growth that occurs in the colon and other organs.  These growths, or fleshy tumors, are shaped like a mushroom or a dome-like button, and occur on the inside lining of the colon.  They may be as small as a tiny pea or larger than a plum.

Colon polyps start out as benign tumors but in time may become malignant.  The larger the polyp, the more likely it is to contain cancer cells.

Why Do Colon Polyps/Cancer Form?

A great deal is known about why and how polyps form.  In some people heredity and genes are the most important factors.  In others, heredity may be necessary but diet and foods may also be very important.

Risk Factors for Colon Polyps/Cancer.

Heredity and genes

Someone with a family history of colon cancer is at a greater risk for developing colon cancer.  For example, someone who had a parent with colon cancer is at roughly double the average risk.  This risk increases as more family members are affected.

In some families the genetic disorder is so strong that it is the only thing that matters.  Hereditory Familial Adenomatous Polyposis (FAP) and Lynch Syndrome (see below) are two disorders that are clearly linked to genes alone.

Most colon cancers (70-75%) however are sporadic - i.e.  there is no family history.

Nongenetic risk factors

Obesity and Exercise

Obesity appears to increase a person’s risk for colon cancer.  The exact amount of this is unknown.  Diabetics may also be at a higher risk, so we believe there may be a role of insulin resistance contributing to a person’s risk for colon cancer.  Exercise is believed to decrease the risk for colon cancer.

Meat

Red meat may increase the risk of colon cancer.  In all likelihood, this is created by the saturated animal fat.  How the meat is prepared may also impact the risk.  For example, charcoal grilling may increase risk by creating potentially cancer-inducing by-products called heterocyclic aromatic amines.  Non-red meat does not seem to be associated with the same risk.  Finally, processed meats may have an increased risk compared to that of fresh meat.  Nitrate compounds in processed meats may contribute to this risk.

Fruit, Vegetables and Fiber

As much as we would like to think these food groups protect our colon, there is unclear benefit.  The studies are conflicting whether they offer any true benefit in reducing a person’s risk for colon cancer.  Of these, vegetables containing antioxidants (cabbage, brussels sprouts, and broccoli) may be most helpful.  We should not, however, lose sight of the clear overall benefit of a diet rich in these food groups.

Calcium

Calcium may be helpful by binding the bile acids in the colon.  Bile acids may contribute to cancer-forming cells and neutralizing them with calcium may help.  We probably need to take at Least 700-800 mg of calcium a day to achieve this benefit.

Antioxidants

There is insufficient information to draw any conclusions of the benefits of antioxidant therapy and colon cancer.  There is one study to suggest that selenium, contained in brewer’s yeast, may be helpful.

Folate

Folate is a vitamin essential in many body functions, including production of our red cells.  It also helps repair DNA.  Cancer cells form and proliferate when there is uncontrolled replication of DNA.  We know that people who are deficient in folate are at a considerably increased risk for colon cancer.  Some studies have shown that if one takes folate for a long period of time, probably more than ten years, you may reduce the chances of developing colon polyps or colon cancer.   A large recent study, however, questioned this conclusion.

Alcohol

Many studies have confirmed that high alcohol intake will increase a person’s risk for colon polyps and cancer.

Tobacco

There has been a longstanding association of tobacco and colon cancer.  More recently, studies have shown that smoking roughly doubles a person’s risk for colon cancer.  It is estimated that between 7000-9000 deaths a year from colon cancer are attributed to smoking.

Aspirin and Anti-Inflammatory Medication

We have long observed that patients with rheumatoid arthritis who take anti-inflammatory medication, such as Ibuprofen, have a reduced likelihood of getting colon polyps and colon cancer.  These medications are even used in some patients at a very high risk for colon cancer, such as those with familial adenomatous polyposis.  These medications work by inhibiting some of the proteins that are felt to increase polyp formation.  It is not, however, recommended to routinely take these agents solely for the purpose of reducing colon polyp formation as the risk of these is probably greater than the benefit gained.  You should consult with your physician to weigh the overall risks and benefits.

Post-Menopausal Hormonal Therapy Hormonal replacement therapy does appear to reduce the risk of colon cancer by 30-40%.  At the same time, hormonal replacement therapy is a complex issue and you should consult with your physician to weigh the risks and benefits of this therapy in your individual case.

In summary, diets high in fruits, vegetables and calcium and low in saturated fats and meats offer the best protection against colon cancer and many other cancers.

Three Categories of Polyps

Enough is now known about polyps that physicians generally place patients in one of three categories.  In each of these the end result is an adenoma type polyp:

1. The Ordinary Polyp—Most sporadic polyps begin to develop between the ages of 40 and 60.  There may be only one or two present and they may take ten years or more to develop into a cancer.  There is a hereditary link.  Eventually some of these become cancer.

2. Hereditary Familial Polyposis—This is a true hereditary condition in which the entire colon is studded with hundreds, even thousands of polyps.  They begin at a very early age even under ten years old.  Virtually every patient will eventually develop colon cancer.  The only known preventive treatment is surgical removal of the colon.  Fortunately, the condition is not common.

3. Lynch Syndrome (Hereditary Non-Polyposis Colorectal Cancer)—This disorder is more common than familial polyposis but less so than the ordinary polyp.  There is a strong tendency for adenoma type polyps to occur in close blood relatives such as sisters, brothers, aunts, uncles and children.  More polyps are seen and at an early age.  Polyps and even cancer occur at earlier ages, 40’s, 30’s and even in the 20’s.  In some families there is also an increased incidence of breast, ovarian, and other cancers.  So a family history of this type warrants very close surveillance of all direct blood relatives.

Detection

The key to early detection of colon polyps and cancer is the concern and willingness of each person to seek medical attention from a physician.  The physician generally will perform the following:

1. Medical history—The patient’s medical history will identify the presence of risk factors for colon polyps and cancer.

2. Stool exams to detect occult (hidden) blood— Colon cancers and large polyps may shed minute quantities of blood so examination of the stool for occult blood is an important exam.

3. Sigmoidoscopy—This is a visual exam of the rectum and lower colon using a lighted, flexible endoscope.  It allows for the direct detection of colon tumors of the closest third of the colon, but not the entire colon.

4. Colonoscopy—This procedure examines the entire 5-6 foot long colon.  The exam is usually done under sedation, It is considered the gold standard and the most definitive exam since colon polyps can be discovered and removed at the same time.

5. Barium Enema—This x-ray exam is an older exam which at times is still useful.  Barium flows into the colon and x-rays are taken which then can outline the shadows of polyps and cancer.  Polyps cannot be removed by this technique.

6. Virtual Colonoscopy—This test is newer.  Studies indicate that it does not pick up small polyps as well as colonoscopy but will find larger polyps, particularly if they are hidden behind folds.  Furthermore, like barium enema, polyps cannot be removed even when they are found.

Prevention

Since your genes cannot be changed, if there is a family history of colon polyps or cancer, a colonoscopy should be performed to remove the polyps before they become malignant.  Calcium, folic acid, and aspirin may have a protective role.  Ask your physician about these.  While dietary fiber and regular exercise are not clearly protective, they play a real role in promoting long-term good health.

Summary

Cancer of the colon is a serious but readily detected malignancy.  Early detection promises a particularly high chance of survival.  Most colon cancers start as polyps, which can usually be removed through a colonoscopic exam.  Today, there is much that can be done to prevent and cure this cancer.  The essential first step involves action by the patient.

 

Note: the information in this section is provided as a supplement to information discussed with your healthcare provider.  It is not intended to serve as a complete description of a particular topic or substitute for a clinic visit.