SCREENING
SERIES
The Importance of Screening: The Case for
Colorectal Cancer
Cynthia B. Morrow, MD, MPH
In 2003, approximately 29,000 women in the United States will die
from colorectal cancer despite the fact that death from this form
of cancer is largely preventable with early detection.1 Screening
for colorectal cancer consistently has been shown to decrease colorectal
cancer mortality. However, results of the 2001 Behavioral Risk Factor
Surveillance System revealed that only 41% of American women aged
50 years or older had used a fecal occult blood test (FOBT) within
the preceding year, or had undergone endoscopic examination of the
lower colon, either with flexible sigmoidoscopy or colonoscopy, within
the previous 10 years.2 Even fewer women
are being screened based on current recommendations of the American
Cancer Society, the Institute for Clinical Performance, and the US
Multisociety Task Force on Colorectal Cancer, a consortium of experts
in the field of gastroenterology.3-5 Fortunately,
there are several screening options available, and clinicians can
play an important role in increasing compliance rates for colorectal
cancer screening in their patient populations.
Colorectal cancer
Colorectal cancer is the second leading cause of cancer-related death
in the United States, with costs of approximately $6.5 billion per
year in treatment alone.6 In 2003, approximately
150,000 Americans, including 75,000 women, will be newly diagnosed
with this disease.1 A woman in the United
States has a 1 in 18 risk of developing colorectal cancer in her
lifetime.7
Colorectal cancer is a good target for screening and prevention programs
for several reasons. First, it is a prevalent form of cancer that
causes significant disability and death. Second, the majority of
colorectal cancers arise from adenomatous polyps that can be detected
by a variety of screening tools prior to cancer development. Third,
removal of such precancerous lesions can prevent colorectal cancer.
Finally, early detection and treatment of asymptomatic cancerous
lesions can reduce death from colorectal cancer. Thus, with the current
screening tests available, health care providers have the ability
to make a great impact on the lives of their patients.
Screening Tests
There are several screening tests available for the early detection
of polyps and colorectal cancer. A patient and her clinician can
choose any one of the following screening tests, with the exception
of digital rectal examination, and be in compliance with current
practice guidelines. Specific recommendations will be addressed in
the following section.
Digital Rectal Examination
Digital rectal examination, even in combination with a single FOBT
of the stool obtained, has a very low sensitivity and specificity
for colon cancer. This should not be used as a screening test.
Fecal Occult Blood Testing
When properly screening for colorectal cancer with FOBT, patients
submit three consecutive samples of stool to be tested for the presence
of blood. Dietary restrictions prior to the screening, such as elimination
of red meat prior to stool collection, are unnecessary according
to a recent meta-analysis that demonstrated such restrictions did
not decrease false-positive results in nonrehydrated samples.8 Hydration
of the specimen prior to testing increases the sensitivity of the
test but decreases the specificity. The current guidelines of the
US Multisociety Task Force on Colorectal Cancer call for stool specimens
to be tested without hydration.5 A positive
test (defined as any positive result on any of the slides) must be
followed by an examination of the entire colon. If all three tests
are negative, annual FOBT screening is recommended.
Fecal occult blood testing is the least expensive and least invasive
screening method for colorectal cancer, but it is also the least
accurate. Despite this limitation, randomized controlled trials have
demonstrated that both annual and biennial use FOBT significantly
decrease colorectal cancer mortality rates.9
Flexible Sigmoidoscopy
This office-based test, which requires minor bowel preparation, involves
endoscopic visualization of the lower portion of the colon. Trained
primary care physicians, as well as gastroenterologists and surgeons,
can perform this test, and sedation is not necessary. Serious complications,
such as bowel perforation, are very rare (1 per 10,000 examinations).10 Abnormal
findings on a flexible sigmoidoscopy often result in evaluation of
the entire colon. If no concerning lesion is revealed, current recommendations
are for repeat sigmoidoscopy every 5 years, although a recent study
by Schoen et al11 questions whether
such screening should occur every 3 years.
Screening using flexible sigmoidoscopy is both more costly and more
invasive than FOBT, though less so than colonoscopy and double-contrast
barium enema (DCBE). Case-control studies have demonstrated that
flexible sigmoidscopy decreases mortality from colorectal cancer,
and randomized controlled trials to support this finding are currently
underway.6
A popular recommendation, based on expert consensus and a nonrandomized
trial, is annual FOBT in combination with flexible sigmoidoscopy
every 5 years.6
Colonoscopy
Colonoscopy involves visualization of the entire colon and requires
thorough bowel preparation prior to the procedure and sedation during
the procedure. Gastroenterologists or surgeons usually perform this
procedure. Serious complications are uncommon (2 to 4 per 1,000),
with bleeding being the most common serious complication when biopsies
are performed.10 If examination reveals
adenomatous polyps and the lesions are completely removed, repeat
surveillance is generally indicated in 3 to 5 years, depending on
the specific findings. If the examination does not reveal any concerning
lesions, next screening colonoscopy is usually recommended at 10
years.
Colonoscopy is more expensive, more invasive, and associated with
more complications than flexible sigmoidoscopy or FOBT. There is
little direct evidence of morbidity or mortality benefit to support
the use of colonoscopy as a screening tool, but lower quality studies,
as well as the fact that colonoscopy is used in the subsequent evaluation
of the less-invasive screening tests (FOBT and sigmoidoscopy), support
the use of colonoscopy as a screening test.
Double Contrast Barium Enema
Screening with a DCBE involves thorough bowel preparation followed
by radiographic examination of barium throughout the entire colon.
Sedation is not necessary and serious complications are very rare
(1 in 10,000).9 If the examination reveals
lesions, a follow-up colonoscopy is recommended. If the examination
does not reveal concerning abnormalities, repeat surveillance is
usually indicated in 5 years.
Double contrast barium enema requires more preparation than flexible
sigmoidoscopy and is more costly, but more of the colon is visualized.
It is less invasive and less costly than colonoscopy. To date, there
is very little trial evidence to support the use of DCBE as a screening
tool.
New Screening Methods
There are several new methods available including “virtual
colonoscopy” and stool-based DNA studies. In “virtual
colonoscopy,” computed tomography or magnetic resonance imaging
studies are used to generate an image of the colon that approximates
what would be seen by colonoscopy. In addition to virtual colonoscopy,
stool-based DNA testing has become available recently as a noninvasive
test for the early detection of colorectal cancer. This test may
reveal changes in cells as they progress from adenomas to carcinomas.
Neither of these tests, however, has been studied extensively enough
to demonstrate whether it is an effective screening tool for colorectal
cancer.
SCREENING RECOMMENDATIONS
The recommendations listed below apply to persons at average risk
for colorectal cancer. Individuals at increased risk should be screened
at an earlier age and more aggressively than indicated in the following
recommendations. Individuals are at increased risk if they have a
personal or family history of adenomatous polyps or of colorectal
cancer, or have one of the familial cancer syndromes, such as familial
adenomatous polyposis or hereditary nonpolyposis colorectal cancer.
Individuals are also at increased risk if they have a personal history
of inflammatory bowel disease.
Guideline Developers
American Cancer Society and the US Multisociety Task Force
on Colorectal Cancer.—The US Multisociety Task Force
on Colorectal Cancer is the committee representing guideline developers,
which includes the American College of Gastroenterology - Medical
Specialty Society; the American College of Physicians - Medical Specialty
Society; the American Gastroenterological Association - Medical Specialty
Society; and the American Society for Gastrointestinal Endoscopy
- Medical Specialty Society. The general colorectal cancer screening
recommendations of the American Cancer Society and the US Multisociety
Task Force are listed in the Table.
Institute for Clinical Systems Improvement.—This
institute’s recommendations are essentially the same as those
outlined in the Table, except that an upper age range of younger
than 80 years is recommended. In addition, a flexible sigmoidoscopy,
in combination with fluoroscopic barium enema, is considered an acceptable
tool for visualization of the entire colon, and the periodicity for
repeat surveillance with colonoscopy is 5 to 10 years.4
US Preventive Services Task Force.—The US
Preventive Services Task Force “strongly recommends that clinicians
screen men and women aged 50 years or older for colorectal cancer” (“A” recommendation).9 It
also reports there is not enough current information available to
determine which is the best screening test.9
The Patient
Screening for colorectal cancer is effective in reducing death and
disability associated with this disease, but the choice of a particular
method of screening can be confusing. The patient and her health
care provider must decide together which screening option is best
for her, taking into account personal and cultural preferences as
well as other existing medical conditions. One woman may prefer the
ease and flexibility of FOBT, while another may prefer the high degree
of accuracy afforded by colonoscopy. A patient with multiple medical
conditions and a life expectancy less than 5 years may reasonably
choose not to undergo screening.
Discussion
Both clinicians and patients are becoming more attuned to the importance
of disease prevention. There is compelling evidence to support screening
as a means for reducing the incidence of, and the mortality from,
colorectal cancer. Unfortunately, as previously discussed, the majority
of American women are not being screened in accordance with current
guidelines. Furthermore, cost-effectiveness analysis has demonstrated
that screening by any of the recommended methods is cost-effective.12 Both
individual- and population-based approaches to improve screening
rates can be effective in early detection of colorectal cancer.
Clinicians have been shown to play a crucial role in the promotion
of colorectal cancer screening,13 and
health care providers must be more aggressive in encouraging and
emphasizing the importance of colorectal cancer screening to their
patients. Clinicians’ offices should be organized to facilitate
screening by having patient education materials available, as well
as providing screening reminders and follow-up letters. Also, they
should have a referral system in place and have an understanding
of insurance coverage for each type of screening test. In addition,
clinicians should be aware of the local capacity in their areas for
each procedure. For example, if local availability of colonoscopy
is limited, it is reasonable to limit referrals for that procedure
to individuals who are symptomatic or who have a positive initial
screening test and require further diagnostic evaluation.
Population-based approaches (eg, media campaigns) also can be used
to promote awareness of the importance of screening for colorectal
cancer. In a recent article in the Archives of Internal Medicine,
Cram et al14 demonstrate that NBC anchorperson
Katie Couric’s public campaign to increase screening for colorectal
cancer was associated with an increase in the number of colonoscopies
performed by a voluntary consortium of gastroenterologists. In this
study, slightly younger individuals and more women (a group consistent
with the demographics of Couric’s television audience) underwent
colonoscopy in the period following the campaign than in the period
prior to the campaign.
CONCLUSION
Screening for colorectal cancer reduces morbidity and mortality in
adults aged 50 years or older. There are several effective screening
methods available for detection of this prevalent disease. Health
care providers should discuss the benefits of prevention and early
detection of colorectal cancer with their patients and present the
different screening options, so that each patient aged 50 years or
older can choose the test that is most appropriate for her.
Cynthia B. Morrow, MD, MPH, is
director of preventive services, Onondaga County Health Department,
Syracuse, New York; and assistant professor, Department of Medicine,
SUNY - Upstate Medical University, Syracuse, NY.
References
- American Cancer Society.
Cancer facts and figures 2003. Available at: http://www.cancer.org/downloads/STT/CAFF2003PWSecured.pdf.
Accessed July 24, 2003.
- Centers for Disease Control
and Prevention. Colorectal cancer: the importance of prevention
and early detection. Available at: http://www.cdc.gov/cancer/colorctl/colorect.
htm#screening. Accessed July 24, 2003.
- American Cancer Society.
American Cancer Society guidelines for the early detection
of colorectal cancer. Available at: http://www.cancer.org/colonmd/pdfs/guidelines.pdf.
Accessed July 21, 2003.
- Institute for Clinical
Systems Improvement. Colorectal cancer screening. Available
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- US Multisociety Task
Force on Colorectal Cancer. Colorectal cancer screening and
surveillance: clinical guidelines and rationale-update based
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Accessed July 31, 2003.
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- Pignone M, Campbell MK,
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Accessed July 21, 2003.
- Davila ML, Keeffe EB.
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- Schoen RE, Pinsky PF,
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- Pignone M, Saha S, Hoerger
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- Cibula DA, Morrow CB.
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- Cram P, Fendrick AM,
Inadomi J, Cowen ME, Carpenter D, Vijan S. The impact of a
celebrity promotional campaign on the use of colon cancer screening:
the Katie Couric effect. Arch Intern Med. 2003;163(13):1601-1605.
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