| Colon
Cancer
Introduction
Colon is the medical term for the large intestine. Colon cancer is the
second leading cause of cancer deaths in the United States, second only
to lung cancer. In 2005, an estimated 104,950 new cases will be diagnosed,
and an estimated 56,290 patients will die of the disease. An individual
has about a one in twenty lifetime risk of developing colon cancer.
Only about three percent of colon cancers occur in persons under age
fourty. Ninty percent of colon cancers occur in patients over age fifty.
In the United States, both incidence and mortality rates are declining.
This decline may reflect better nutrition and possibly removal of polyps
from the colon before they have had a chance to turn into cancer.
Risk Factors
Risk factors for colon cancer are as follows:
Family history of colon cancer.
Familial adenomatous polyposis.
Hereditary nonpolyposis colon cancer.
Having a diet high is animal fat.
Low dietary fiber in the diet.
Having ulcerative colitis or Crohn's disease.
Having three or more alcoholic drinks per day.
Cigarette smoking.
Elevated C-reactive protein that is a blood test.
Well-established risk factors for colon cancer are high dietary fat
intake and heredity. Animal fat has the highest association with colon
cancer. About 15 percent of all colon cancer patients have a family
history of colon cancer in a first-degree relative. Low dietary fiber
is also associated with a higher risk of colon cancer. Fiber seems to
dilute the cancer-causing substances (carcinogens) in the stool and
therefore the bowel wall has less exposure to the carcinogens. A sedentary
lifestyle and obesity are both correlated with an increased risk of
colon cancer. Interestingly, removal of the gallbladder is associated
with a small increase in colon cancer in females. Excessive alcohol
intake has also been associated with an increased risk of colon cancer.
Reducing your risk
Diets that are high in fruits and vegetables are associated with a lower
colon cancer risk.
Regular physical exercise decreases your chance of getting colon cancer
by 50 %.
Increasing dietary fiber in your diet.
Reducing your intake of animal fat may reduce your risk of colon cancer.
Taking aspirin or other anti-inflammatory (like ibuprofen) medication
daily.
Taking folic acid daily.
Increasing dietary calcium intake.
Statins seem to have a protective effect.
Estrogen replacement therapy lowers the risk of colon cancer.
Dietary fat should constitute less than 30 percent of total caloric
intake. Dietary fiber should exceed 20 grams each day. Your diet should
be rich in vegetables and fruits. Alcohol consumption should be no more
than two drinks per day for males and one drink a day for females. Exercise
has been shown to reduce the risk of colon cancer by 50 percent. Taking
an aspirin as few as three times a week has been shown to reduce the
incidence of colon cancer by 30 percent. Increasing the amount of vitamin
D and calcium in the diet may reduce your risk of developing colon cancer.
Taking a multivitamin everyday would provide folic acid.
Symptoms of Colon Cancer
Colon cancer may be present for years before any symptoms develop. This
is because colon cancer develops over several stages. Polyps develop
first and slowly turn into a cancerous growth. This progression of events
usually takes around 7-10 years. This makes colon cancer amenable to
being diagnosed at an early stage when it is preventable (removing polyps)
or completely curable. Symptoms of colon cancer are:
Rectal bleeding.
Change in bowel habit.
Abdominal pain.
Unexplained anemia.
Rectal bleeding requires an evaluation by your physician. Don't assume
that the blood is from hemorrhoids. Many patients that I diagnose with
colon cancer have a history of rectal bleeding. They assumed the rectal
bleeding was due to their hemorrhoids and delayed seeking treatment.
Screening for Colon Cancer
Several options are available for colon cancer screening:
Annual fecal occult blood test (FOBT). This is commonly referred to
as stool cards.
Sigmoidoscopy exam every five years beginning at age 50 along with annual
stool cards.
Colonoscopy exam every ten years beginning at age 50 along with annual
stools cards.
Barium enema every five years. This method of screening has lost favor
over the past decade.
A sigmoidoscopy consists of inserting a fiber optic tube into the rectum
and directly examining the bowel wall. It is about 2 feet long and doesn't
require sedation. The colonoscopy consists of a 7 foot fiber optic tube
that allows visualizing the entire colon. A colonoscopy is preferred
if you have a family history of colon cancer or if you have rectal bleeding.
The FOBT should be done yearly beginning at age 50 even if a colonoscopy
is performed. FOBT can detect colon cancers that may have been missed
by the colonoscopy. The colonoscopy is quite good at detecting polyps
and colon cancer but it is not perfect. The colon is tortuous and has
numerous folds that can hide a polyp or cancer from even the most experienced
gastroenterologist. Screening should begin earlier if there are any
significant risk factors for colon cancer. Studies have shown that a
yearly fecal occult blood test by itself can actually reduce the death
rate from colon cancer by 33 percent. Having a sigmoidoscopy every five
years along with yearly stool cards will reduce your chances of dying
of colon cancer by around 70%. Having a colonoscopy every ten years
has not been proven to reduce the death rate but most physicians feel
it will reduce the death rate significantly greater than 70%. Colonoscopies
are associated with a higher complication rate than sigmoidoscopies.
If a first-degree relative has had colon cancer, then screening should
begin at age 35 or 10 years younger than the age the relative was first
diagnosed. A digital rectal exam should be performed every year beginning
at age 50 for all males and females.
Treatment
If the cancer is confined to a polyp, then the chances of cure are extremely
good. Radiation therapy is also used to treat colon cancer. Chemotherapy
has been shown to reduce recurrences and improve survival. The five
year survival is rate is 61 % in the United States according to the
National Cancer Institute.
References
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The information provided above is offered as a community service about
health-care issues and is not a substitute for individual consultation.
Advice on individual problems should be obtained from your personal
physician. This information is based on research by the author and represents
his interpretation of the literature.
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Readers may send questions to our
email address. This column is for informational purposes only and
is not a substitute for professional or medical advice.
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