| Colon
Cancer |
| What
is Colon Cancer? |
 |
|
By
Miriam Komaromy,
MD
Reviewed
by Peggy Conrad,
MS, CGC and Jonathan
Terdiman, MD
Last
updated July 21, 2000
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Colon
cancer is one of the most common types of cancer. Because
cancer can occur in both the colon and rectum, cancer
statistics usually group colon and rectal cancer together.
Thus, this type of cancer is more accurately referred
to as colorectal cancer although we will refer to it
as colon cancer for simplicity sake.
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Who
Gets Colon Cancer?
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In
the developed world, three percent to five percent of
the population will eventually be diagnosed with colon
cancer. In the United States alone, the disease accounts
for a full 14 percent of all deaths from cancer, making
it the second most common cause of cancer death.
 |
| Colon
cancer is the second leading cause of cancer death
in the US. |
|
When worldwide colon cancer cases are studied, equal numbers of men and women develop colon cancer. However, in those geographic regions where the disease is more frequently detected — for example, the United States — more men than women are diagnosed. The average age of onset is 64. (For recent news about who gets colon cancer, see Related News below.) |
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Where Does Colon Cancer Begin?
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Colon
cancer is a solid cancerous growth that begins on the
inner surface of the colon or rectum. Virtually all colon
cancer develops from mushroom-like growths (called adenomatous
polyps) that can grow on the inside wall of the colon.These
polyps can be quite small or extremely large.  The
larger a polyp is, the greater the likelihood that it
will become cancerous. For the most part, it takes years
for a polyp to become cancerous, and in fact most polyps
never do. Researchers estimate that one in four people
has developed adenomatous polyps by the age of 50, though
most of these people will never develop colon cancer.
 |
Click
image for larger
representation
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Once
a polyp does
turn into colon cancer, however it often grows quickly.
As
it enlarges, it can block the colon, invade and break
through the colon wall, or eventually spread to other
parts of the body. |
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Signs
and Symptoms
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Some
of the signs of colon cancer include rectal bleeding,
unexplained weight loss, constipation or diarrhea, abdominal
pain, and a marked decrease in the diameter of your stools
(that is, your stools become more narrow, and typically
longer in length). colon cancer can also result in anemia,
or a low red blood cell count. If a cancer becomes large
enough, it can block the colon, giving rise to intense
abdominal pain and preventing bowel movements.
 |
Click
image for larger
representation
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However,
it's important to note that colon cancer often fails to
produce any symptoms until the cancer has grown very large
or even metastasized (spread)
to other parts of the body. This is why the identification
and subsequent removal of polyps through regular screening
plays such an important role in colon cancer prevention.
Because both polyps and cancers tend to bleed, doctors
can first try testing the stools of the subject for trace
amounts of blood. If blood is found, the doctor can then
perform either a sigmoidoscopy
or colonoscopy.
These procedures allow a doctor to look through a lighted
tube at the inside walls of your colon and remove polyps—in
essence stopping the cancer before it begins. |
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Factors
That Increase Your Risk
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Colon
Cancer Signs and Symptoms:
 Rectal
bleeding (red or black stools)
Unexplained
weight loss
New
constipation or diarrhea
Abdominal
pain
Stools
becoming long or narrow
Anemia
(low red blood count) |
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There
are a number of factors — both genetic and nongenetic
— that appear to increase your chance of developing
colon cancer.
Individuals who have already been diagnosed with inflammatory
bowel disease (NOT irritable bowel disease) are at increased
risk for colon cancer. In addition, other nongenetic
factors include increasing age, above-average consumption
of red meat, a high-fat or low-fiber diet, obesity,
a sedentary lifestyle, and smoking. Thus, changes in
your lifestyle may be able to reduce your risk of develoing
colon cancer.
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Among
those members of the population who seem to be genetically
predisposed to the disease (that is, individuals who
have family members who have been diagnosed with colon
cancer), researchers have identified alterations, or
mutations, in several genes that increase the likelihood
of developing colon cancer. Some of these mutations
increase risk only slightly, and others make an eventual
diagnosis of colon cancer nearly inevitable. These latter
types of mutations are said to cause hereditary colon
cancer syndromes, the most common of which are hereditary
nonpolyposis colorectal cancer (HNPCC), and familial
adenomatous polyposis (FAP).
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You
can use our TreeBuilder tool to learn whether your family
history puts you at increased risk for colon cancer.
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Screening
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| All
adults 50 years of age or older should be regularly
screened for colon cancer. |
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All
adults more than 50 years old should be screened for colon
cancer since regular screening has been shown to reduce
colon cancer deaths. People who are at increased risk
of developing colon cancer have different screening recommendations
than the general public. For example, screening can begin
at a younger age; may take place more frequently, and
require the use of different procedures.
The
precise screening recommendations depend on a person's
level of risk. Some factors that should prompt more aggressive
screening include family history of colon cancer or polyps;
a previous personal diagnosis of inflammatory bowel disease,
or a previous personal diagnosis of either colon cancer
or polyps. |
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Treatment
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If
you have been diagnosed with colon cancer, your treatment
will depend on the location, size, and spread of your
cancer at the time of diagnosis. When colon cancer is
detected at an early stage, surgical treatment is highly
effective. Doctors also sometimes use chemotherapy or
radiation in along with surgery to reduce the chance that
the cancer will return.
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 top
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Links
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If
you want to learn more about treatment options for colon
cancer, we recommend the National Institutes of Health
Cancer Page which can be found at: http://cancernet.nci.nih.gov
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References
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Potter,
J. (1999). Colorectal cancer: molecules and populations.
J Natl Cancer Inst 91(11): 916-32.
Winawer, S. et al. (1996). Risk of colorectal cancer
in famillies of patients with adenomatous polyps: National
Polyp Study Workgroup. N Engl J Med 334: 82-87.
Winawer, S. (1999). Natural history of colorectal cancer.
Am J Med 106(1a): 3S-6S.
Winawer, S. et al. (1997). Colorectal cancer screening:
clinical guidelines and rationale. Gastroeneterology
112: 594-642
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