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Patient Education
Colon cancer
Definition:
The colon and
rectum are part of the large intestine (large
bowel). Colon and rectum cancers, which are
sometimes referred to together as "colorectal
cancer," arise from the lining of the large
intestine. When cancer arises from the lining of
an organ like the large intestine, it is called
a
carcinoma.
Other types of
colon cancer are rare, and include
lymphoma, carcinoid tumors,
melanoma, and sarcomas. Use of the term
colon cancer for the rest of this article refers
to colon carcinoma and not the other, more rare
types of colon cancer.
Causes,
incidence, and risk factors:
There are over 130,000 cases of colorectal
cancer diagnosed in the United States each year,
and over 50,000 deaths. Colorectal cancer is the
second leading cause of cancer deaths. In almost
all cases, however, this disease is entirely
treatable if caught early by colonoscopy.
There is no single cause for colon cancer.
However, almost all colon cancers begin as
benign polyps which, over a period of many
years, develop into cancers.
Factors that increase the risk of colon cancer
are
colorectal polyps, cancer elsewhere in the
body, a family history of colon cancer, and
ulcerative colitis.
Patients with a history of breast cancer have a
slightly increased risk of developing colon
cancer. Certain genetic syndromes increase the
risk of developing colon cancer in affected
families.
Dietary factors that have been associated with
colon cancer are a high-meat,
high-fat, low-fiber diet. However, some
studies found that the risk is not reduced when
people switch to a high-fiber diet, so the cause
of the link is not yet clear.
Symptoms:
With proper screening, colon cancer should be
detected BEFORE the development of symptoms,
when it is most curable.
Most cases of colon cancer have no symptoms. The
following symptoms, however, may indicate colon
cancer:
Signs and
tests:
A physical examination rarely shows any
abnormalities, although an abdominal mass may be
present. A rectal examination may reveal a mass
in patients with rectal cancer, but not colon
cancer.
A
colonoscopy or
sigmoidoscopy may reveal evidence of cancer.
However, only colonoscopy (NOT sigmoidoscopy)
examines the entire colon.
A
fecal occult blood test (FOBT) may detect
small amounts of blood in the stool, a possible
indicator of colon cancer. However, this test is
often negative in patients with colon cancer.
Not all polyps bleed, and not all polyps bleed
all the time. That is why a FOBT must be used
with one of the other more invasive screening
measures, either colonoscopy or sigmoidoscopy.
Finally, a positive FOBT doesn't necessarily
mean the person has cancer -- "false positives"
may be caused by some medications and other
factors.
A blood count may reveal evidence of anemia with
low iron levels. A CT scan may show an abdominal
mass, although this test is not very good at
detecting colon cancer.
Treatment:
Treatment depends partly on the stage of the
cancer. This means how far the tumor has spread
through the layers of the intestine, from the
innermost lining to outside the intestinal wall
and beyond:
-
Stage 0: Very
early cancer on the innermost layer (more
accurately considered a precursor to cancer)
-
Stage I: Tumor in
the inner layers of the colon
-
Stage II: Tumor
has spread through the muscle wall of the
colon
-
Stage III: Tumor
that has spread to the lymph nodes
-
Stage IV: Tumor
that has spread to distant organs
Stage 0 colon cancer may be treated by cutting
out the lesion, often via a colonoscopy. For
stages I, II, and III cancer, more extensive
surgery to remove a segment of colon containing
the tumor and reattachment of the colon is
necessary. (See
colon resection.) This procedure only rarely
requires a colostomy.
Almost all patients with stage III colon cancer,
after surgery, should receive chemotherapy
(adjuvant chemotherapy) with a drug known as
5-fluorouracil given for approximately 6 - 8
months. This drug has been shown to increase the
chance of a cure. There is some debate as to
whether patients with stage II colon cancer
should receive chemotherapy after surgery, and
patients should discuss this with their
oncologist.
Chemotherapy is also used for patients with
stage IV disease in order to shrink the tumor,
lengthen life, and improve the patient's quality
of life. Irinotecan, oxaloplatin, and
5-fluorouracil are the 3 most commonly used
drugs, given either individually or in
combination. There are oral chemotherapy drugs
which are similar to 5-fluroruracil, the most
commonly used being capecitabine (Xeloda).
Oxaliplatin, a newer chemotherapy drug, was
approved by the FDA in 2002 and is also active
against colon cancer. It is often used in
combination with 5-fluorouracil, and studies are
being done that combine it with other
chemotherapy drugs. Other chemotherapy agents,
including drugs that specifically target
abnormalities in cancer cells, are currently in
development and undergoing clinical trials.
For patients with stage IV disease that is
localized to the liver, various treatments
directed specifically at the liver can be used.
Tumors may be surgically removed, burned, or
frozen in some cases. Chemotherapy or
radioactive substances can sometimes be infused
directly into the liver.
Radiation therapy is occasionally used in
patients with colon cancer, but this is often
used in combination with chemotherapy for
patients with stage III rectal cancer.
Expectations (prognosis):If
the patient's colon cancer does not come back
(recur) within 5 years, it is considered cured.
This is because colon cancer rarely comes back
after 5 years. Stage I, II, and III cancers are
considered potentially curable. In most cases,
stage IV cancer is not curable.
Stage I has a 90% 5-year survival. Stage II has
a 75 - 85% 5-year survival, and Stage III a 40 -
60% 5-year survival. These numbers take into
account that for stage III patients (and in some
studies, stage II patients), chemotherapy
improves the chance of 5-year survival.
Patients with stage IV disease rarely live
beyond 5 years, and the median survival (meaning
half the patients live longer, and half shorter)
with treatment is between 1 and 2 years.
Complications:
-
Cancer spreading
to other organs or tissues (metastasis)
-
Recurrence of
carcinoma within the colon
-
Development of a
second primary colorectal cancer
Calling your health
care provider:
Colon cancer is, in almost all cases, a
treatable disease if caught early. Removal of
premalignant polyps by colonoscopy essentially
prevents colon cancer. Any man or woman age 50
or over who has not had a colonoscopy should
call his or her physician to schedule one.
Additionally, call your physician if you develop
blood in the stool (either visible blood or
blood detected by a
home fecal occult blood test), black tarry
stool, or a change in bowel habits. However, it
is important to emphasize that most people with
colon cancer have no symptoms.
Prevention:
Approximately 50,000 people die of colon cancer
every year. Yet, colon cancer can almost always
be caught in its earliest and most curable
stages by colonosocopy. Almost all men and women
age 50 and older should have a colonoscopy.
Colonoscopy is almost always painless and most
patients are asleep for the entire procedure.
Taking laxatives and/or enemas before the test
to clean out the colon isn't fun, but most
people find this to be the worst part of the
procedure. It may be embarrassing or awkward,
but it is certainly better than having cancer.
Certain people may require colonoscopies before
age 50. These include persons with a history of
colon polyps or inflammatory bowel disease, and
people with a first degree relative (mother,
father, brother or sister) with colon cancer
that developed before the age of 60.
Additionally, patients with personal or family
history of other types of cancer may need to
consider colon cancer screening at an earlier
age.
Fecal occult blood test, sigmoidoscopy, and
barium enema are other screening tests that can
be used for early detection and prevention of
colon cancer, but colonoscopy remains the gold
standard.
A new test, a virtual colonoscopy, uses CT scan
technology to visualize the colon. There are
several problems with this test, however. First,
it is early in development and we still don't
have enough information to determine how
accurate it really is. Second, patients must
take a preparation the night before to clean out
the colon. Finally, if an abnormality is seen,
the patient must still undergo a traditional
colonoscopy.
Dietary and lifestyle modifications are
important. Some evidence suggests that low-fat
and high-fiber diets may reduce your risk of
colon cancer. However, even patients who follow
strict diets can develop this disease and
require colonoscopy.
Some evidence suggests that non-steroidal
anti-inflammatory drugs (NSAIDs) may help
prevent colon cancer, but again, screening is
still necessary.
Colon
cancer - resources
The
following organizations are good resources for
information on colon cancer:
Colorectal Cancer Network
PO Box 182
Kensington, MD 20895-0182
301-879-1500
www.colorectal-cancer.net
Colon Cancer Alliance
175 Ninth Avenue
New York, NY 10011
212-627-7451
www.ccalliance.org
Cancer Care
275 7th Avenue
New York, NY 10001
800-813-HOPE
www.cancercare.org
American Cancer Society
800-ACS-2345
www.cancer.org |
