What is the risk of colorectal cancer?
Colorectal cancer is the second most common
cancer in the United States. The average person's lifetime risk
of developing it is about one chance in 20. The risk is
increased if there is a family history of colorectal polyps or
cancer, and is still higher if there is a personal history of
breast, uterine or ovarian cancer. Risk is also higher for
people with a history of extensive inflammatory bowel disease,
such as ulcerative or Crohn's colitis.
What is screening and surveillance?
Many polyps and cancers of the colon and rectum do not
produce symptoms until they become fairly large. Screening
involves one or more tests performed to identify whether a
person with no symptoms has a disease or condition that may lead
to colon or rectal cancer. The goal is to identify the potential
for disease or the condition early when it is easier to prevent
or cure. Surveillance involves testing people who have
previously had colorectal cancer or are at increased risk.
Because their chance of having cancer is higher, more extensive
or more frequent tests are recommended.
Later in the brochure, the tests and risk groups are defined.
Also, your physician can further explain the tests and their
value to you.
Why should testing be undertaken?
Colorectal cancer is known as a "silent"
disease, because many people do not develop symptoms, such as
bleeding or abdominal pain until the cancer is difficult to
cure. In fact, the possibility of curing patients after symptoms
develop is only about 50%. On the other hand, if colorectal
cancer is found and treated at an early stage, before symptoms
develop, the opportunity to cure is 80% or better. Most colon
cancers start as non cancerous growths called polyps. If the
polyps are removed, then the cancer may be prevented. Major
surgery can usually be avoided.
What screening tests should be done?
The simplest screening test for colon and rectal
cancer is testing of the stool to detect tiny amounts of
invisible blood; this is called fecal occult blood testing.This
test has been available for many years, is inexpensive and very
simple. Unfortunately, it only detects cancer or polyps which
are bleeding at the time of the test. Only about 50% of cancers
and 10% of polyps bleed enough to be detected by this test.
Therefore, further screening is necessary for accurate detection
of cancers and polyps.
Flexible sigmoidoscopy is a test which allows
the physician to look directly at the lining of the colon and
rectum. During this test, which is performed in the physician's
office, the lining of the lower one-third of the colon and
rectum can usually be seen. This is the portion of the lower
intestine which accounts for most polyps and cancers. When
flexible sigmoidoscopy is combined with testing the stool for
hidden blood, many cancers and polyps can be detected.
When a polyp or cancer is detected by flexible
sigmoidoscopy, or if a person is at high risk to develop colon
and rectal cancer, colonoscopy provides a safe, effective means
of visually examining the full lining of the colon and rectum.
Colonoscopy is used to diagnose colon and rectal problems and to
perform biopsies and remove colon polyps. Most colonoscopies are
done on an outpatient basis with minimal inconvenience and
discomfort.
A barium enema or x-ray of the colon is almost
as good as colonoscopy in detecting large tumors, but it is not
as accurate for small tumors or polyps. The combination of
barium enema and sigmoidoscopy is better than either test alone,
but not as good as colonoscopy.
When and how often should testing be done?
For people who have none of the risks described
earlier, digital rectal examination and testing of the stool for
hidden blood are recommended annually beginning at age 40.
Flexible sigmoidoscopy is recommended every 5 years at age 50 or
older. A double contrast barium enema every 5 to 10 years, and
colonoscopy every 10 years are acceptable alternatives.
Surveillance is recommended for people in the
following high-risk groups:
-
People who have had any pre-cancerous polyps
found and removed should have colonoscopy one to three years
after the first examination. Double-contrast barium enema is
an alternative to colonoscopy but does not allow removal of
polyps.
-
People with a close relative, such as
sibling, parent or child who has had colorectal cancer or a
pre-cancerous polyp should have the same screening as people
of average risk, but it should begin at age 40 or 5 years
before the age at which the youngest was diagnosed.
-
People with a family history of colorectal
cancer in several close relatives and several generations,
especially cancers occurring at a young age, should receive
genetic counseling and consider genetic testing for a
condition called hereditary nonpolyposis colorectal cancer.
People with this family medical history should have an
examination of the entire colon preferably colonoscopy every
two years starting between the age of 20 and 30, and every
year after age 40.
-
People with a family history of an inherited
disease called familial adenomatous polyposis (FAP) should
receive counseling and consider genetic testing to see if
they are carriers for the gene that causes the disease.
People with this gene or whose tests are inconclusive should
have a flexible sigmoidoscopy annually beginning at puberty
to see if they are expressing the gene. If polyposis is
present, they should discuss with their physician the need
for total colectomy, which involves removing all the colon
and rectum.
-
People with a personal history of colorectal
cancer should have a complete examination of the colon
within one year after the cancer is initially detected and
surgically removed. If this exam is normal, they should have
a follow-up exam within three years. Examinations to
evaluate the entire colon include colonoscopy or flexible
sigmoidoscopy with adouble-contrast barium enema.
-
People with a history of extensive
inflammatory bowel disease for 8 or more years should
consider having a colonoscopy examination of their colon
conducted every one to two years.
-
Women with a personal history of breast or
female genital cancer (ovary or uterine) have a 15% lifetime
risk (1 in 6) of developing colon cancer. They should
undergo colonoscopy every 5 years, beginning at age 40.
Who does the screening and surveillance?
The simpler tests such as digital rectal
examination, fecal occult blood testing, or flexible
sigmoidoscopy may be performed by your primary care physician or
your surgeon. They can also arrange for colonoscopy to be
performed by a specially trained physician, such as a colon and
rectal surgeon.
