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Colon Cancer

By Dr. Peter W. Kujtan, B.Sc., M.D., Ph.D.

This article appeared under a different title on page 12 in the October 16-17, 2004 issue of
The Mississauga News: Health & Wellness, Doctor's Corner
Dr K

I find it peculiar that MRI seems to have become an acronym used to measure affluence in the health care system. How many of these machines and how long does it take to get a study done seems to misleadingly dictate how healthy our system is. This is deceiving, and there are many other important parameters that factor in. Colonoscopy is one of these.

Colon or bowel cancer is cancer arising in the large intestine, and is a topic close to my heart. It is the third leading cause of cancer death in Canada, and we also have the highest rate in the world. We divide it into genetic and non-genetic. HNPCC stands for Hereditary Non-polyposis colorectal cancer. It is caused by genetic mistakes in coding for enzymes that monitor other genetic mistakes. The other genetic type is called Familial Adenomatous Polyposis. In this type, hundreds of polyps develop in the colon. One popular hypothesis suggests that most colon cancer arises from a polyp. These small tissue tags which grow from the intestinal wall often go on to transform into colon cancer. In the small percentage of people who have identified genetic bowel cancer in their families, there exist highly specific genetic tests that can identify if they too have inherited these cancer-causing genes. This group of individuals will require intensive screening, because they have a 50% chance of inheriting the genes.

Most of the colon cancer is non-genetic. Age is a risk factor, and diet is also implicated. The cancer rate goes from 1 in a 1000 for 39-year-olds to 1 in 125 when you hit 50. Bowel and food go together. It is the first point of contact of partially digested food for absorption. It also places it as an ideal contact point for toxins and carcinogens hoping to enter the body. The cells lining this structure are constantly multiplying. This is significant because cell division is a time when mistakes in coding can be made which is the first step towards abnormality. The large intestine also recycles water and concentrates stool. A diet high in junk, preservatives and other substances produces a stool concentrated in these substances also.

In the early stages of colon cancer there are no significant symptoms. There is also no blood test that leads to early detection. Physical symptoms such as rectal bleeding, weight loss, bloating, fatigue, and change in stool habits should at least trigger a consultation. The first test that will be ordered will be a blood test to check the stool for microscopic blood (called the Fecal Occult Stool Test). The rationale is that the bowel tumor may be a source of microscopic bleeding, and the microscopic blood will show up in the stool or may cause the serum hemoglobin to drop. We cannot exclude numerous other causes with these tests. The next test often ordered is called a Double-Contrast Barium Enema. It consists of bowel x-rays taken after an enema of chalky substance is instilled to coat the bowel walls. It is able to show larger tumors and polyps, but can miss small ones. The current gold standard for diagnosis is a colonoscopy. In this test, a small flexible fiber-optic camera is introduced into the rectum after the intestines are emptied of all contents. It is passed up through the large intestine and the area is directly visualized to look for abnormalities. This procedure has the advantage of allowing the doctor to conduct a biopsy on any suspected lesions or even completely excise polyps.

In Ontario, the Fecal Occult Stool Test is the most common screening method used. Present dictum suggests that persons over 50 should have it done every 2 years. It is an ancient test that turns positive under many other circumstances such as having hemorrhoids, non-cancerous disorders, even menstruation, or after having consumed beets. A positive test combined with symptoms in someone over 50 may result in a colonoscopy. This procedure is performed in a special clinic usually located at a hospital. Colonoscopy is expensive, and sadly, we probably do not have enough qualified gastroenterologist and colonoscopy facilities to serve the rising demand. It is an excellent test to look for colon cancer, but like everything else, it is not a sure thing. It is also worth noting that there are two other non-funded tests that are very good. The first is spiral CAT Scan. A special CAT-scan machine is combined with enhanced software to produce a virtual tour of the colon. It is not available in Canada. The second one is. In this test, a microscopic camera is loaded into a tiny capsule which is swallowed. As it travels through the intestine, it sends images to a belt-pack that are later reviewed. The downside is that it needs to be repeated for a closer look or biopsy. In the end, the pros and cons of colonoscopy are not written in stone. It is worth sitting down with your doctor and together reviewing what your best course of action is. Or better yet, as Dr.Hollingworth loves to tell me, bend over and smile! For more information on cancer treatment visit Ontario Cancer Trials.ca.


Colors of Cancer Google image from http://qwickstep.com/search/the-colors-of-cancer.html
The Colors of Cancer
See Cancer Color Card

Related resources:

What Is Colorectal Cancer - Do you want to know what bowel cancer is? from Colon Cancer Concern (CCC), UK

Overview: Colon and Rectum Cancer from American Cancer Society

Colorectal Cancer Network: Mission: To Eliminate Colon Cancer and Support Patients

All About Colon and Rectum Cancer from American Cancer Society

Colorectal Cancer from MedlinePlus

Colon Cancer from eMedicine Health

Colon Cancer: The Basics; Rectal Cancer: The Basics from Oncolink

Colon Polyps and Cancer from Jackson Gastroenterology with illustrations

Colon Cancer (Colorectal Cancer) - Colon cancer information on causes, symptoms, tests to detect cancer of the colon from MedicineNet

Additional resources for colorectal cancer from American Cancer Society.

What Are the Symptoms of Colon Cancer? Medical Author: Dennis Lee, MD. Medical Editor: Jay W. Marks, MD.

The high school student who devised a cure for cancer ... YouTube video, 3:28 min.

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