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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
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. It is becoming increasingly
clear that certain of these genes control the growth of the cells
on the lining of the colon. 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 from 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. It is
important to note that while colon polyps start out as benign
tumors, some polyps, in time, become malignant. In fact, the
larger the polyp, the more likely it is to contain cancer cells.
In most cases, it is a polyp called an adenoma polyp that
develops into colon cancer.
What are the Risk Factors For Developing Colon Polyps and
Cancer?
- Family history of polyps, cancer and especially, colon cancer
- Western civilization and diet
- Being over 40 years of age
- History of breast cancer
- Ulcerative colitis
An individual whose parents, brothers or sisters have colon
cancer is at increased risk. In addition, certain unusual
conditions, such as hereditary polyposis, lead to colon cancer
100 percent of the time. Persons living and eating in Western
societies are exposed to certain factors that are detrimental to
the bowel. Medicine is just beginning to learn about these. Also,
females who have had genital or breast cancer are at an increased
risk of developing colon cancer. Ulcerative colitis, after a long
time, also can lead to colon malignancy.
Why Do Polyps Form?
 As noted above heredity is probably the
most important factor. The absence of a controlling gene within
the cells is most likely a necessary event.
Other facts are known. Rural residents in Africa and India
rarely develop colon polyps or cancer. Their diets are high in
unprocessed grains (bran) and low in meat. Diets that are high in
bran and roughage produce bulky stools that have a lower bacteria
count. Further, it is known that animal fat in meat, when broken
down by the body's intestinal juices, may change into certain
compounds termed carcinogens. These compounds cause colon cancer
in laboratory animals. When residents in developing countries eat
a Westernized diet of meat, low roughage and refined grains, over
time they develop the same incidence of colon polyps and cancer
as people living in the Western world. So diet probably plays an
important role in causing colon cancer.
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 sporatic polyps occur 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.
2. 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. And virtually every patient will eventually develop colon
cancer. The only known preventive treatment is removal of the
colon. Fortunately, the condition is not common.
3. Lynch Syndrome-Dr. Lynch first described this hereditary
disorder. It is more common than familial polyposis and less so
than the ordinary polyp. In it there is a strong tendency for
adenoma type polyps to develop 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 can occur in the
30's and even 20's. In some families there is 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 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 release minute quantities of blood; therefore,
examination of the stool for occult blood is an important
exam.
3. Sigmoidoscopy-A visual exam of the rectum and lower colon,
using a lighted, rigid or flexible tube, or endoscope, allows the
direct detection of colon tumors.
4. Colonoscopy-This procedure examines the entire 5-6 foot
long colon. Physicians perform it when any of the above three
detection methods suggests a problem. The exam is usually done
under sedation. It is really the definitive test since colon
polyps can be discovered and removed at the same time.
5. Barium Enema-This x-ray exam is an older, at times still
useful, exam. 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. Future tests-It is possible that a blood genetic test may
become available to identify those individuals who are destined
to develop colon polyps and cancer.
How are Polyps Removed?
Removal of colon polyps reduces the risk of subsequent
development of cancer of the colon. Polyps are usually removed
using a colonoscope, which allows the physician to visualize the
inside of the colon. Biopsy equipment and snares (wire loops) are
passed through the endoscope and, with electrical heat
(electrocautery), remove polyps and small tumors. This procedure
is performed in the outpatient setting under sedation.
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.
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