Statements & Guidelines
This document, adopted by SAGES, was circulated during the
recent SADDW Colorectal Campaign…….
People with symptoms or signs that suggest the presence of
colorectal cancer or polyps should be offered the
appropriate diagnostic evaluation.
Screening programmes should begin by classifying the
individual patients level of risk based on personal, family
and medical history, which will determine the appropriate
approach to screening in that person.
Men and women at average risk should be offered screening
for colorectal cancer from age 50.
They should be offered options for screening after being
given information about the advantages and disadvantages of
each method, and should be given an opportunity to apply
their own preference in selecting how they should be
An abnormal screening test must be followed by a complete
examination of the colon, preferably by colonoscopy (or
flexible sigmoidoscopy and double contrast barium enema if
colonoscopy is not available.)
Individuals at increased risk should be by means of
colonoscopy. This group includes:
- Those with previous colorectal cancer
- History of prior adenomatous polyps
Patients with an underlying condition which predisposes
to colorectal cancer e.g. inflammatory bowel disease
Health care providers performing these tests should have
appropriate proficiency, and the tests should be performed
correctly. Standards and operating procedures should be set.
Screening must be accompanied by efforts to optimise the
participation of patients and health care providers, both in
the initial screening and in the rescreening at recommended
Screening Average Risk Individuals
Faecal Occult Blood Testing
Yearly or biennial faecal occult blood testing (FOBT) has
been shown to reduce colorectal cancer mortality by 21%.
Drawbacks of this method of screening include low compliance
rates, high false positive rates leading to colonoscopy with
its associated cost, discomfort and complications, and high
false negative rates. Depending on the type of test used
patients may require dietary restriction such as avoiding
red meat. This may further reduce compliance.
The finding of a positive faecal occult blood test should
result in a colonoscopy being performed, as this examination
is superior in accuracy to double contrast barium enema.
Sigmoidoscopy performed every 5 years has been shown to
reduce colorectal cancer deaths by up to two thirds for
lesions within reach of the sigmoidoscope. Cancer risk above
this level was not reduced. Repeat screening every 5 years
has been shown to be optimal. This is less than the interval
for colonoscopy, and reflects the lower sensitivity of
sigmoidoscopy, from examining less of the colon, but also a
less thorough examination as bowel preparation is often
sub-optimal, varied experience of examiners, and the effect
of patient discomfort limiting the depth of insertion of the
Having found an adenoma on sigmoidoscopy, the decision to
proceed to colonoscopy should be individualized. Studies
have shown that positive sigmoidoscopy followed by
colonoscopy would detect 70-80% of advanced proximal
neoplasia, and reduce cancer incidence by 80%.
Combined FOBT and Flexible Sigmoidoscopy
Annual FOBT and 5 yearly sigmoidoscopy is yet another method
of screening for colorectal cancer. This approach has now
been studied in a randomised control trial. Sigmoidoscopy
detected 70% of patients with advanced neoplasia, and the
addition of a one-time FOBT increased the rate to 76%.
Another study showed a significant additional yield by
adding sigmoidoscopy to FOBT testing. Three times as many
cancers and 5 times as many large adenomatous polyps were
identified in the combined group. When this method of
screening is used, the FOBT must be done first, as a
positive FOBT is an indication for colonoscopy.
The disadvantages of this approach are the additional costs,
inconvenience and complications of both tests with an
uncertain gain in effectiveness.
Colonoscopy is able to detect lesions in both distal and
proximal colon, and one has the possibility of removing
polyps found at this examination. An interval of 10 years
between examinations after a negative colonoscopy is
recommended. This is based on the finding that the dwell
time from the development of adenomatous polyps to
transformation to cancer is estimated to be at least 10
years on average. Fewer than 6% of clinically important
adenomas are missed at colonoscopy. Recent studies have
confirmed that 50% to 65% of patients with advanced proximal
neoplasia had no distal colonic neoplasms.
The costs, inconvenience and complications need to be
considered in advising colonoscopy as a screening method.
Colonoscopy may not be widely available, and expertise in
performing the examination varies widely.
Double-Contrast Barium Enema
Double-contrast barium enema (DCBE) offered every 5 years
has been used for colorectal cancer screening. DCBE has
lower sensitivity than colonoscopy for detecting cancers and
large polyps, and the examination does not permit removal of
polyps, or biopsy of cancers. False positive examinations
may occur due to presence of stool. An abnormal DCBE must be
followed by colonoscopy.
DCBE is offered because of lower cost, examination of the
whole colon, wide availability, and detection of about half
of large polyps. The combination of DCBE and sigmoidoscopy
is not recommended for screening.
In a surveillance population DCBE detected 53% of
adenomatous polyps 6-10mm in size, and 48% of adenomas >1cm
The “average risk” of colorectal cancer in the western world
is estimated at 6%. Screening strategies have been shown to
prevent the risk of colorectal cancer. The challenge is to
communicate this knowledge to the wider public, to health
care providers and funders, and then to complete the
Colorectal cancer screening is more complex than screening
for breast and cervical cancer, where one type of test is
required (mammography, Pap smear).
For screening to be successful doctors must remember to
offer screening, patients must accept this advice, insurers
must pay for screening and follow-up testing, and
patient-care organisations must have systems to track
whether screening has taken place and to give reminders if
it has not.
Advanced colorectal cancer is a devastating disease, and is
preventable with appropriate screening methods. It is with
this in mind that the South African Gastroenterology Society
(SAGES) and its allied professional groups, is embarking on
a colorectal cancer prevention campaign. The aim is to reach
the health care professionals, the public at risk and the
funders to heighten awareness, and to stimulate action. The
initiative will culminate during the South African Digestive
Diseases Week (SADDW) in August 2003.
The source of this article is largely from the American
Society of Gastroenterology Guideline published in
Gastroenterology in February 2003.