Arkansas Diagnostic Center

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What Is Cancer? Cancer occurs when cells in a part of the body begin to grow out of control. Normal cells divide and grow in an orderly fashion, but cancer cells do not. They continue to grow and crowd out normal cells. Although there are many kinds of cancer, they all have in common this out-of-control growth of cells. Different kinds of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is aimed at their kind of cancer. Sometimes cancer cells break away from a tumor and spread to other parts of the body through the blood or lymph system. They can settle in new places and form new tumors. When this happens, it is called metastasis (meh-tas-tuh-sis). Cancer that has spread in this way is called metastatic cancer. Even when cancer has spread to a new place in the body, it is still named after the part of the body where it started. For example, if prostate cancer spreads to the bones, it is still called prostate cancer. If breast cancer spreads to the lungs, it is still breast cancer. When cancer comes back in a person who appeared to be free of the disease after treatment, it is called a recurrence.

Colorectal cancer is a term used to refer to cancer that starts in the colon or rectum. Colon and rectal cancers begin in the digestive system, also called the GI (gastrointestinal) system. This is where food is processed to create energy and rid the body of waste matter.

After food is chewed and swallowed, it travels down to the stomach. There it is partly broken down and sent to the small intestine. The word "small" refers to the diameter of the small intestine. The small intestine is really the longest segment of the digestive system. It is about 20 feet long.

The small intestine continues breaking down the food and absorbs most of the nutrients. The small intestine joins the large intestine (large bowel), a muscular tube about five feet long. The first part of the large bowel, called the colon, absorbs water and nutrients from the food and also serves as a storage place for waste matter. The waste matter moves from the colon into the rectum, the final 6 inches of the large bowel. From there the waste passes out of the body through the opening called the anus during a bowel movement.

Cancer can start in any of the four sections or in the rectum. The wall of each of these sections (and rectum) has several layers of tissues. Cancer starts in the inner layer and can grow through some or all of the other layers. Knowing a little about these layers is helpful because the stage (extent of spread) of a cancer depends to a great degree on which of these layers it affects.

Cancer that starts in the different areas may cause different symptoms. In most cases, colon and rectum cancers develop slowly over a period of several years. We now know that most of these cancers begin as a polyp a growth of tissue into the center of the colon or rectum. A type of polyp known as adenomacan become cancerous. Removing the polyp early may prevent it from becoming cancer.

Over 95% of colon and rectal cancers are adenocarcinomas. These are cancers of the cells that line the inside of the colon and rectum. There are some other, more rare, types of tumors of the colon and rectum, but the facts given here refer only to adenocarcinomas.
Colon and rectal cancer have many features in common and are often referred to simply as colorectal cancer.

Other than skin cancer, colorectal cancer is the third most common cancer found in men and women in this country. The American Cancer Society estimates that there will be about 106,680 new cases of colon cancer and 41,930 new cases of rectal cancer in 2006 in the United States. Combined, they will cause about 55,170 deaths.

The death rate from colorectal cancer has been going down for the past 15 years. One reason is that there are fewer cases. Thanks to colorectal cancer screening, polyps can be found and removed before they turn into cancer. And colorectal cancer can also be found earlier when it is easier to cure. Treatments have improved as well.

Screening tests are used to look for disease in people who do not have any symptoms. In many cases, these tests can find colorectal cancers at an early stage and greatly improve the chances of successful treatment. Screening tests can also help prevent some cancers by allowing doctors to find and remove polyps that might become cancer. There are several tests used for colorectal cancer.

Stool blood test (fecal occult blood test FOBT): This test is used to find small amounts of hidden (occult) blood in the stool. A sample of stool is tested for traces of blood. People having this test will receive a kit with instructions that explain how to take stool samples at home. The kit is then sent to a lab for testing. If the test is positive, further tests, such as a colonoscopy, will be done to pinpoint the exact cause of the bleeding.

A newer kind of stool blood test is known as FIT (fecal immunochemical test). It is very much like the FOBT but is perhaps a little easier to do and it gives a fewer number of false positive results. If it is positive, further tests will be done.
Flexible sigmoidoscopy (flex-sig): A sigmoidoscope is a slender, lighted tube about the thickness of a finger. It is placed into the lower part of the colon through the rectum. This allows the doctor to look at the inside of the rectum and part of the colon for cancer or polyps. Because the tube is only about 2 feet long, the doctor is only able to see about half of the colon. The test can be uncomfortable but it should not be painful. Before the test, you will need to take an enema to clean out the lower colon.

Colonoscopy: A colonoscope is a longer version of the sigmoidoscope. It allows the doctor to see the entire colon. If a polyp is found, the doctor may remove it. If anything else looks abnormal, a biopsy might be done. To do this, a small piece of tissue is taken out through the colonoscope. The tissue is sent to the lab to see if cancer cells are present. This test can be uncomfortable. To avoid this, you will be given medicine through a vein to make you feel relaxed and sleepy.

Medicare now covers these two tests for people at average risk who have Medicare coverage. More details can be found by calling us."
Barium enema with air contrast: A chalky substance is used to partly fill and open up the colon. Air is then pumped in to cause the colon to expand. This allows good x-ray films to be taken. You will need to use laxatives the night before the exam and have an enema the morning of the exam.

Virtual colonoscopy: You might think of this as a super x-ray of the colon. Air is pumped into the colon to cause it to expand, and then a special CT scan is done. Right now, this test is not among those recommended by the ACS or other major medical organizations for finding colon cancer early. More studies are needed to find out if it is as good as or better than other methods of finding colon cancer early.