SCREENING FOR COLORECTAL CANCER
Guidelines
1. American Gastroenterological Association (AGA). Colorectal cancer
screening: clinical guidelines and rationale.
<http://www.guideline.gov/FRAMESETS/guideline_fs.asp?guideline=0045>
Gastroenterology 1997 Oct;113(4):1423-4 [220 references].
2. U.S. Preventive Services Task Force (USPSTF). Screening for
colorectal cancer.
<http://www.guideline.gov/FRAMESETS/guideline_fs.asp?guideline=0152> In:
Guide to clinical preventive services. 2nd ed. Baltimore (MD): Williams &
Wilkins, 1996. p. 89-103 [113 references].
3. American Cancer Society (ACS). American Cancer Society guidelines
on screening and surveillance for the early detection of adenomatous polyps
and cancer-update 2001.
<http://www.guideline.gov/FRAMESETS/guideline_fs.asp?guideline=1974> In:
American Cancer Society guidelines for the early detection of cancer. CA
Cancer J Clin 2001 Jan-Feb;51(1):44-54 [181 references].
4. Institute for Clinical Systems Improvement (ICSI). Colorectal
cancer screening.
<http://www.guideline.gov/FRAMESETS/guideline_fs.asp?guideline=1476>
Bloomington (MN): Institute for Clinical Systems Improvement (ICSI); 2000
Jan. 24 p. [49 references].
5. Canadian Task Force on Preventive Health Care (CTFPHC). Preventive
Health Care, 2001 Update: colorectal Cancer Screening.
<http://www.guideline.gov/FRAMESETS/guideline_fs.asp?guideline=2120> CMAJ
2001; 165(1):206-7 [97 references].
INTRODUCTION:
A direct comparison of AGA, USPSTF, ACS, ICSI, and CTFPHC recommendations
for screening asymptomatic individuals and individuals at increased risk for
colorectal cancer is provided in the following tables. In formulating their
recommendations, ACS and CTFPHC review the conclusions drawn by AGA and
USPSTF. ICSI considers the guideline released by USPSTF. Following the
content comparison, areas of agreement and differences among the guidelines
are discussed. In general, the timing of the guideline with respect to
available data is an important factor to consider when evaluating areas of
differences among guidelines. The rationale behind differences in practice
recommendations that cannot be attributed to differences in the evidence
base is also discussed.
The evidence supporting the major recommendations is also identified, with
the definitions of the rating schemes used by USPSTF, ICSI and CTFPHC
included in the last row of the table.
Abbreviations used in the text and tables follow:
* ACS, American Cancer Society
* AGA, American Gastroenterological Association
* CRC, colorectal cancer
* CTFPHC, Canadian Task Force on Preventive Health Care
* DCBE, double contrast barium enema
* DRE, digital rectal examination
* FOBT, fecal occult blood testing
* HNPCC, hereditary nonpolyposis colorectal cancer
* ICSI, Institute for Clinical Systems Improvement
* TCE, total colon examination
* USPSTF, United States Preventive Services Task Force
OBJECTIVE AND SCOPE
AGA
(October, 1997)
* To develop practical screening and surveillance guidelines for colorectal
cancer (CRC) in average- and high-risk populations
USPSTF
(1996)
* To present screening guidelines for colorectal cancer in adults at average
and increased risk
ACS
(2001)
* To address growing evidence concerning the benefits of early detection of
colorectal cancer and adenomatous polyps
ICSI
(2000)
* To reduce variation in screening for colorectal cancer (CRC)
* To eliminate wasteful, unproductive processes for CRC screening
* To increase patient participation in screening for CRC
CTFPHC
(2001)
* To make recommendations on the effectiveness of specific screening
techniques for colorectal cancer in asymptomatic patients
INTENDED USERS
AGA
(October, 1997)
Primary care clinicians and specialists
USPSTF
(1996)
Primary care clinicians
ACS
(2001)
Primary care clinicians and specialists
ICSI
(2000)
Primary care clinicians
CTFPHC
(2001)
Primary care clinicians and specialists
INTERVENTIONS AND PRACTICES CONSIDERED
AGA
(October, 1997)
Screening options:
1. Fecal occult blood testing (FOBT), flexible sigmoidoscopy, or both
2. Digital rectal examination (DRE) [Not recommended as the sole screening
test but as a part of a screening examination]
3. Double contrast barium enema (DCBE)
4. Colonoscopy
Recommendations for high risk populations (i.e., counseling for genetic
testing)
USPSTF
(1996)
Screening options:
1. Fecal occult blood testing (FOBT), or sigmoidoscopy, or both
2. Digital rectal examination (DRE) [Not recommended as the sole screening
test]
3. Double contrast barium enema (DCBE)
4. Colonoscopy
High-risk patients are outside the scope of this guideline
ACS
(2001)
Screening options:
1. Fecal occult blood testing (FOBT) or flexible sigmoidoscopy, or both
2. Digital rectal examination (DRE) [Not recommended as the sole screening
test but prior to sigmoidoscopy or colonoscopy]
3. Double contrast barium enema (DCBE)
4. Colonoscopy
Recommendations for high risk populations (i.e., counseling for genetic
testing)
ICSI
(2000)
Screening options:
1. Fecal occult blood testing (FOBT), flexible sigmoidoscopy, or both
2. Digital rectal examination (DRE) [Not recommended as the sole screening
test but as a part of a health evaluation]
3. Double contrast barium enema (DCBE)
4. Colonoscopy
High-risk patients are outside the scope of this guideline
CTFPHC
(2001)
Screening options:
1. Fecal occult blood testing (FOBT), flexible sigmoidoscopy, or both as a
part of multiphase screening
2. Colonoscopy as a part of uniphase screening
3. Genetic testing
Screening with digital rectal examination and double contrast barium enema
were not considered because of the lack of direct evidence
COMPARISON OF RECOMMENDATIONS FOR SCREENING FOR COLORECTAL CANCER:
ADULTS, > 50 YEARS, NO OTHER RISK FACTORS
Fecal occult blood testing (FOBT)
AGA
(October, 1997)
* An acceptable screening option is to offer FOBT on annual basis. This
option is supported by strong evidence of effectiveness.
USPSTF
(1996)
* Screening is recommended, based on fair evidence. Both FOBT and
sigmoidoscopy are effective screening methods. There is insufficient
evidence to determine which method is preferable.
* There is good evidence to support FOBT on an annual basis.(B, II-1, II-2)
ACS
(2001)
* FOBT annually is an acceptable screening option.
* The take-home multiple sample method should be used.
ICSI
(2000)
* An acceptable screening option is FOBT annually. (Evidence supporting the
screening recommendations is of classes: C, R, B, D)
CTFPHC
(2001)
* There is good evidence to include screening with Hemoccult test in the
periodic health examination of asymptomatic patients over age 50 with no
other risk factors [A, I].
However, there remain concerns about the high rate of false-positive
results, feasibility and small clinical benefit of such screening (over 1000
individuals must be screened for 10 years to avert one death from colorectal
cancer). For patients being screened with Hemoccult, it is recommended that
they avoid red meat, cantaloupe and melons, raw turnip, radishes, broccoli
and cauliflower, vitamin C supplements and aspirin and non-steroidal
anti-inflammatory drugs for 3 days before fecal samples are collected.
However, a recent meta-analysis of 4 randomized controlled trials found no
improvement in positivity rates or change in compliance rates with moderate
dietary restrictions.
Flexible sigmoidoscopy
AGA
(October, 1997)
An acceptable screening option is to offer sigmoidoscopy every five years.
This option is supported by strong evidence of effectiveness. A five year
interval is chosen because of strong (randomized trial) evidence that
colonoscopy is equally effective at 1- or 1- and 3- year intervals, weaker
(case control) evidence that sigmoidoscopy is effective at up to 10-year
intervals, and the observation that few polyps arise and progress to
advanced cancer in a 5 year period.
USPSTF
(1996)
Sigmoidoscopy is considered an effective screening technique; however, there
is insufficient evidence to recommend a periodicity for sigmoidoscopy
screening. (I-2, II-3)
ACS
(2001)
Flexible sigmoidoscopy performed every 5 years is an acceptable screening
option.
This recommendation is supported by case-control studies of clinical
effectiveness. The five year interval is chosen because of a range of
factors that may affect the overall sensitivity of flexible sigmoidoscopy:
* Flexible sigmoidoscopy is generally not done by specialists and thus the
range of practitioner experience and expertise is variable.
* Bowel preparation usually is less complete than for colonoscopy, meaning
that important lesions may be obscured by stool.
* Because no sedation is given with flexible sigmoidoscopy, patient
discomfort or spasm may interfere with the completeness of the test.
ICSI
(2000)
An acceptable screening option is 60 cm flexible sigmoidoscopy every 5
years. (Evidence supporting the screening recommendations is of classes: C,
R, B, D)
CTFPHC
(2001)
There is evidence from case control studies, to recommend that flexible
sigmoidoscopy be included in the periodic health examination of patients
over age 50 [B, II-2, III].
Combined fecal occult blood testing and flexible sigmoidoscopy
AGA
(October, 1997)
The individual components of this strategy are supported by strong evidence
but the added value of combining the two, while theoretically present, is
not well established by research evidence. Indirect evidence, including the
panel’s decision analysis on the clinical consequences of CRC, supports this
recommendation.
USPSTF
(1996)
There is insufficient evidence to determine whether this combination of
tests produces greater benefits than either test alone.
ACS
(2001)
FOBT every year plus flexible sigmoidoscopy every 5 years is an acceptable
screening option.
Because combining flexible sigmoidoscopy with FOBT can increase the benefits
of either test alone, the ACS regards annual FOBT accompanied by flexible
sigmoidoscopy every five years as a better choice than either FOBT or
flexible sigmoidoscopy alone.
ICSI
(2000)
An acceptable screening option is a combination of both 60 cm flex
sigmoidoscopy every 5 years and FOBT annually. (Evidence supporting the
screening recommendations is of classes: C, R, B, D)
CTFPHC
(2001)
There is insufficient evidence to make recommendations about whether only 1
or both of FOBT and sigmoidoscopy should be performed [C, I].
Digital rectal examination (DRE)
AGA
(October, 1997)
DRE by itself has not been shown to be an effective way of screening for
CRC.
However, it is part of other screening examinations for CRC (sigmoidoscopy,
colonoscopy, and barium enema) and may be included in a comprehensive
program of preventive health care for other reasons.
USPSTF
(1996)
DRE is of limited value as a screening test for CRC. There is insufficient
evidence to recommend for or against routine screening with DRE.
Recommendations against using this test may be made on other grounds (e.g.,
availability of alternate tests of proven effectiveness, inaccuracy of DRE).
(C, III)
ACS
(2001)
Although DRE is a useful method for identifying masses in the anal canal or
lower rectum, it has very poor sensitivity for detecting colorectal cancer
due to limited reach. While DRE is often included as part of a routine
physical examination, it is not recommended as a stand-alone screening test
for colorectal cancer. However, DRE should be performed prior to insertion
of a sigmoidoscope or colonoscope.
ICSI
(2000)
DRE is a simple examination to perform with potential to discover a small
percentage of colon cancers within reach of the examining finger. Palpation
of any mass or polyp should lead to further investigation.
Separate health care encounters for the sole purpose of doing a DRE are not
suggested. A DRE might be performed as part of a visit for either health
evaluation or illness-related concerns.
CTFPHC
(2001)
Screening with digital rectal examination was not considered because of the
lack of direct evidence.
Barium enema
AGA
(October, 1997)
An acceptable screening option is double contrast barium enema (DCBE) every
5-10 years.
This option is not supported by direct evidence (from randomized trial,
nonrandomized trial, or case-control studies) that DCBE reduces mortality
from CRC; but it is supported by the panel’s decision analysis on the
clinical consequence of CRC.
USPSTF
(1996)
There is insufficient evidence to recommend for or against routine screening
with barium enema.
Recommendations against using this test for screening average-risk persons
may be made on other grounds (e.g., availability of alternate tests of
proven effectiveness). (C, III)
ACS
(2001)
Examining the entire colorectum, either by colonoscopy every 10 years or by
DCBE every 5 years is an acceptable screening option.
The choice of colonoscopy or DCBE for screening can be made on an individual
basis, depending on factors such as personal preference, cost, feasibility,
tolerance of potential complications, and the local availability of trained
clinicians able to offer a high-quality examination. For those who elect
either colonoscopy or DCBE for screening, there is no need for annual FOBT.
ICSI
(2000)
Acceptable screening option: perform total colon examination by flexible
sigmoidoscopy combined with fluoroscopic barium enema or DCBE every 5 years.
(Evidence supporting the screening recommendations is of classes: C, R, B,
D)
CTFPHC
(2001)
Screening with double contrast barium enema was not considered because of
the lack of direct evidence.
Colonoscopy
AGA
(October, 1997)
An acceptable screening option is colonoscopy every 10 years.
This option is not supported by direct evidence (from randomized trial,
nonrandomized trial, or case-control studies) that colonoscopy reduces
mortality from CRC; but it is supported by other evidence and the panel’s
decision analysis on the clinical consequence of CRC.
USPSTF
(1996)
There is insufficient evidence to recommend for or against routine screening
with colonoscopy.
Recommendations against using this test for screening average-risk persons
may be made on other grounds (e.g., availability of alternate tests of
proven effectiveness, costs and risks of colonoscopy). (C, III)
ACS
(2001)
Examining the entire colorectum, either by colonoscopy every 10 years or by
DCBE every five years is an acceptable screening option.
The choice of colonoscopy or DCBE for screening can be made on an individual
basis, depending on factors such as personal preference, cost, feasibility,
tolerance of potential complications, and the local availability of trained
clinicians able to offer a high-quality examination. For those who elect
either colonoscopy or DCBE for screening, there is no need for annual FOBT.
ICSI
(2000)
An acceptable screening option is total colon examination, by colonoscopy
every 5-10 years (Evidence supporting the screening recommendations is of
classes: C, R, B, D)
CTFPHC
(2001)
There is insufficient evidence to include or exclude colonoscopy as an
initial screen in the periodic health examination [C, II-3].
Although colonoscopy is the best method for detecting adenomas and
carcinomas, it may not be feasible to screen asymptomatic patients because
of patient compliance and the expertise and equipment required and the
potential costs. On the other hand, if colonoscopy were an effective
screening strategy when performed at less frequent intervals, these issues
might be of less concern.
COMPARISON OF RECOMMENDATIONS FOR SCREENING FOR COLORECTAL CANCER:
PEOPLE AT INCREASED RISK FOR COLORECTAL CANCER
People with family history of colorectal cancer
AGA
(October, 1997)
People with a close relative (sibling, parent or child) who has had
colorectal cancer or an adenomatous polyp should be offered the same options
as average-risk people but beginning at age 40 years.
If the close relative was diagnosed with colorectal cancer before the age of
55 years or with an adenomatous polyp before age 60, special efforts should
be made to assure that screening takes place.
USPSTF
(1996)
The increased risk of developing cancer at younger ages may justify
beginning screening before age 50 (no specific age stated) in persons with a
single first-degree relative with colon cancer, especially when affected
relative developed CRC at younger ages.
ACS
(2001)
People with a family history of either colorectal cancer or colorectal
adenomas that occurred in a first-degree relative before age 60, or in
multiple first-degree relatives of any age (if not a hereditary syndrome),
should have a colonoscopy* at age 40, or 10 years before the youngest case
in the immediate family. Examination should be repeated every 5-10 years.
Colorectal cancer in relatives more distant than first-degree does not
increase risk substantially above the average risk group.
*Note: If a colonoscopy is not available, not feasible, or not desired by
the patient, a DCBE, or flexible sigmoidoscopy followed by a DCBE can be
used.
ICSI
(2000)
Patients at increased risk of developing colorectal cancer require
colonoscopic surveillance at a 3 to 5 year interval, and are outside the
scope of this guideline.
CTFPHC
(2001)
Patients who have only one or two first-degree relatives with colorectal
cancer should be screened in the same way as average risk individuals. There
is insufficient evidence to recommend colonoscopy for individuals who have a
family history of colorectal polyps or cancer but do not fit the criteria
for hereditary non-polyposis colon cancer [C, III]. While there is evidence
that there is an increased prevalence of neoplasms in these individuals,
there is insufficient information to recommend more intense screening than
that of individuals at average risk. Further delineation of the risk for
individuals with multiple affected family members and family members with
early age of diagnosis of colorectal cancer is necessary.
People with a family history of familial adenomatous polyposis
AGA
(October, 1997)
Genetic counseling and consider genetic testing to see if they are gene
carriers. Gene carriers or indeterminate cases should be offered flexible
sigmoidoscopy every 12 months beginning at puberty to see if they are
expressing the gene. If polyposis is present, they should begin to consider
when they should have colectomy.
USPSTF
(1996)
Refer to specialist for regular endoscopic screening, diagnosis and
management.
ACS
(2001)
Individuals with a family history of familial adenomatous polyposis are at
high risk and should undergo early surveillance with endoscopy, and
counseling to consider genetic testing beginning at puberty. If the genetic
test is positive, colectomy is indicated; These patients are best referred
to a center with experience in the management of familial adenomatous
polyposis.
ICSI
(2000)
Patients at increased risk of developing colorectal cancer require
colonoscopic surveillance at a 3 to 5 year interval, and are outside the
scope of this guideline.
CTFPHC
(2001)
The Task Force recommends genetic testing of individuals at risk for
familial adenomatous polyposis if the genetic mutation has been identified
in the family and if genetic testing is available [B, II-3]. If the
individual carries the mutation, then he or she should be screened with
flexible sigmoidoscopy beginning at puberty [B, II-3]. Individuals from
families where the gene mutation has been identified but are negative
themselves, require screening similar to the average risk population. For at
risk individuals where the mutation has not been identified in the family or
where genetic testing is not available, screening with annual or biannual
flexible sigmoidoscopy should be undertaken beginning at puberty. In all
instances, genetic counseling should be performed prior to genetic testing.
People with a family history of hereditary nonpolyposis colorectal cancer
(HNPCC)
AGA
(October, 1997)
Genetic counseling and consider genetic testing for HNPCC. Offer an
examination of the entire colon every 1-2 years starting between the ages of
20 and 30 years and every year after age 40 years.
USPSTF
(1996)
Refer to specialist for regular endoscopic screening, diagnosis and
management.
ACS
(2001)
Individuals with a family history of HNPCC should undergo colonoscopy and
counseling to consider genetic testing beginning at age 21. If the genetic
test is positive or if patient has not had genetic testing, colonoscopy is
recommended every 1-2 years until age 40 years, then annually. These
patients are best referred to a center with experience in the management of
HNPCC.
ICSI
(2000)
Patients at increased risk of developing colorectal cancer require
colonoscopic surveillance at a 3 to 5 year interval, and are outside the
scope of this guideline.
CTFPHC
(2001)
Patients in kindreds with the cancer family syndrome (HNPCC) have a high
risk of colorectal cancer and a high incidence of right-sided colon cancer.
Thus, colonoscopy rather than sigmoidoscopy is recommended for screening
such patients. Based on Level III evidence, the Task Force recommends
screening with colonoscopy in individuals from hereditary non-polyposis
colon cancer kindreds [B, II-3]. Although higher levels of evidence are
usually required to give a B recommendation, the Task Force realizes that it
is unlikely that more rigorous studies could be performed in this cohort of
patients given the high risk of cancer and relative infrequency of
hereditary non-polyposis colon cancer. The ages when screening should begin
and the frequency at which colonoscopy should be performed are unclear.
People with a history of adenomatous polyps
AGA
(October, 1997)
Patients in whom large (>1-cm diameter) or multiple adenomatous polyps are
found and removed at colonoscopy should have an examination of the colon 3
years after the initial examination. The interval for subsequent
examinations depends on the type of polyps that were detected. If the first
follow-up is normal or only a single, small, tubular adenoma is found, the
next examination can be in 5 years. In special circumstances (e.g., polyps
with invasive cancer, large sessile adenomas, or numerous adenomas), a
shorter interval may be necessary, according to the judgment of the
clinician and the wishes of the patient.
USPSTF
(1996)
Refer to specialist for regular endoscopic screening, diagnosis and
management.
ACS
(2001)
People who have been diagnosed as having adenomatous polyps should have a
colonoscopy to remove all polyps from the colorectum, after which a
colonoscopic exam should be repeated at an interval to be determined on the
basis of the size, multiplicity, and histologic appearance of the
adenoma(s).
* People with single, small (<1 cm) adenoma should be screened with
colonoscopy* 3-6 years after the initial polypectomy. If the exam is normal,
the patient can thereafter be screened as per average risk guidelines (see
above).
* People with a large (1 cm +) adenoma, multiple adenomas, or adenomas with
high-grade dysplasia or villous change should be screened with colonoscopy*
within 3 years after the initial polypectomy. If normal, repeat examination
in 3 years; If normal then, the patient can thereafter be screened as per
average risk guidelines (see above).
*Note: If a colonoscopy is not available, not feasible, or not desired by
the patient, a DCBE, or flexible sigmoidoscopy followed by a DCBE can be
used.
ICSI
(2000)
Patients at increased risk of developing colorectal cancer require
colonoscopic surveillance at a 3 to 5 year interval, and are outside the
scope of this guideline.
CTFPHC
(2001)
People with a history of adenomatous polyps are beyond the scope of the
guideline.
People with a history of colorectal cancer
AGA
(October, 1997)
Patients with a colorectal cancer that has been resected with curative
intent (but who did not undergo complete adequate colonoscopic examination
preoperatively) should have a complete examination of the colon within 1
year after resection. If this or a complete preoperative examination is
normal, subsequent examination should be offered after 3 years and then, if
normal, every 5 years.
USPSTF
(1996)
Refer to specialist for regular endoscopic screening, diagnosis and
management.
ACS
(2001)
Individuals with a personal history of curative-intent resection of
colorectal cancer are at increased risk. Colonoscopy* is recommended within
1 year after resection. If normal, repeat examination in 3 years; if normal
then, repeat examination every 5 years.
*Note: If a colonoscopy is not available, not feasible, or not desired by
the patient, a DCBE, or flexible sigmoidoscopy followed by a DCBE can be
used.
ICSI
(2000)
Patients at increased risk of developing colorectal cancer require
colonoscopic surveillance at a 3 to 5 year interval, and are outside the
scope of this guideline.
CTFPHC
(2001)
People with a history of colorectal cancer are beyond the scope of the
guideline.
People with inflammatory bowel disease
AGA
(October, 1997)
Surveillance colonoscopy, looking for dysplasia as a marker of colorectal
cancer risk, should be considered along with the extent and duration of the
disease as a guide to when or if colectomy should be considered.
USPSTF
(1996)
Refer to specialist for regular endoscopic screening, diagnosis and
management.
ACS
(2001)
Individuals with inflammatory bowel disease, chronic ulcerative colitis, or
Crohn’s disease are at high risk. Colonoscopies with biopsies for dysplasia
are recommended 8 years after the start of pancolitis; 12-15 years after the
start of left-sided colitis. Examination should be repeated every 1-2 years.
These patients are best referred to a center with experience in the
surveillance and management of inflammatory bowel disease.
ICSI
(2000)
Patients at increase risk of developing colorectal cancer require
colonoscopic surveillance at a 3 to 5 year interval, and are outside the
scope of this guideline.
CTFPHC
(2001)
People with inflammatory bowel disease are beyond the scope of the
guideline.
EVIDENCE RATING SCHEMES
Rating Scheme
USPSTF
(1996)
Levels of Evidence
In grading the quality of evidence, the Task Force gave greater weight to
those study designs that, for methodologic reasons, are less subject to bias
and inferential error. The following rating system was used:
I: Evidence obtained from at least one properly randomized controlled trial.
II-1: Evidence obtained from well-designed controlled trials without
randomization.
II-2: Evidence obtained from well-designed cohort or case-control analytic
studies, preferably from more than one center or research group.
II-3: Evidence obtained from multiple time series with or without the
intervention. Dramatic results in uncontrolled experiments (such as the
results of the introduction of penicillin treatment in the 1940s) could also
be regarded as this type of evidence.
III: Opinions of respected authorities, based on clinical experience;
descriptive studies and case reports; or reports of expert committees.
Well-designed and well-conducted meta-analyses were also considered, and
were graded according to the quality of the studies on which the analyses
were based (e.g., Grade I if the meta-analysis pooled properly randomized
controlled trials).
Recommendation Grade
The strength of the recommendation for or against a preventive intervention
was graded as follows:
A: There is good evidence to support the recommendation that the condition
be specifically considered in a periodic health examination.
B: There is fair evidence to support the recommendation that the condition
be specifically considered in a periodic health examination.
C: There is insufficient evidence to recommend for or against the inclusion
of the condition in a periodic health examination, but recommendations may
be made on other grounds.
D: There is fair evidence to support the recommendation that the condition
be excluded from consideration in a periodic health examination.
E: There is good evidence to support the recommendation that the condition
be excluded from consideration in a periodic health examination.
ICSI
(2000)
Evidence Grading System: Classes of Research Reports
A. Primary Reports of New Data Collection:
Class A
* Randomized, controlled trial
Class B
* Cohort study
Class C
* Non-randomized trial with concurrent or historical controls
* Case-control study
* Study of sensitivity and specificity of a diagnostic test
* Population-based descriptive study
Class D
* Cross-sectional study
* Case series
* Case report
B. Reports that Synthesize or Reflect upon Collections of Primary Reports
Class M
* Meta-analysis
* Decision analysis
* Cost-benefit analysis
* Cost-effectiveness study
Class R
* Review article
* Consensus statement
* Consensus report
Class X
* Medical opinion
CTFPHC
(2001)
Level of Evidence:
I - Evidence from at least 1 properly randomized controlled trial (RCT).
II-1 - Evidence from well-designed controlled trials without randomization.
II-2 - Evidence from well-designed cohort or case-control analytic studies,
preferably from more than 1 centre or research group.
II-3 - Evidence from comparisons between times or places with or without the
intervention. Dramatic results in uncontrolled experiments could also be
included here.
III - Opinions of respected authorities, based on clinical experience,
descriptive studies or reports of expert committees.
Recommendation Grade:
A. Good evidence to support the recommendation that the condition or
manoeuvre be specifically considered in a periodic health examination (PHE).
B. Fair evidence to support the recommendation that the condition or
manoeuvre be specifically considered in a periodic health examination.
C. Insufficient evidence regarding inclusion or exclusion of the condition
or manoeuvre in a periodic health examination, but recommendations may be
made on other grounds.
D. Fair evidence to support the recommendation that the condition or
manoeuvre be specifically excluded from consideration in a periodic health
examination.
E. Good evidence to support the recommendation that the condition or
manoeuvre be specifically excluded from a periodic health examination.
GUIDELINE CONTENT COMPARISON
The American Gastroenterological Association (AGA), the U.S. Preventive
Services Task Force (USPSTF), the American Cancer Society (ACS), the
Institute for Clinical Systems Improvement (ICSI), and the Canadian Task
Force on Preventive Health Care (CTFPHC) present recommendations for
screening for colorectal cancer in people at average risk (asymptomatic, age
> 50 years, no other risk factors) and provide explicit reasoning behind
their judgments. The AGA, ACS, and CTFPHC also present screening
recommendations for individuals at increased risk of colorectal cancer.
Because the USPSTF and ICSI guidelines are intended for primary care
clinicians and surveillance of high-risk populations requires referral to a
specialist, further recommendations are not offered for these high-risk
groups by the USPSTF and ICSI.
Areas of Agreement
The AGA, USPSTF, ACS, ICSI, and CTFPHC agree that asymptomatic adults > 50
years, with no other risk factors, should be screened for colorectal cancer,
utilizing one of several acceptable screening tests such as fecal occult
blood testing or flexible sigmoidoscopy. All five groups present two or more
acceptable screening options and do not explicitly recommend one screening
test over another. The ACS suggests that, whenever possible, patients
participate in a shared decision-making process, where information about
each of the screening options, such as accuracy, cost, potential for
prevention, discomfort and risk is discussed. Similarly, the AGA concludes
that decisions about which test or tests to use should take into account the
patient’s preferences, the patient’s age, any existing comorbidity, and
local resources and expertise. The USPSTF also recommends consideration of
patient preferences and patient education in decision making rather than a
uniform policy for all patients.
Due to several obstacles in the shared decision-making approach, such as
availability of well trained personnel and the time it takes to explain
options to patients, ACS acknowledges that clinicians may be able to
successfully implement only one or two of the screening modalities, limiting
options for patients. Consequently, ACS notes that of primary importance at
this time is that clinicians recommend at least one of the appropriate
screening options for all of their eligible patients.
The organizations acknowledge that the option of total colon examination
(TCE) by colonoscopy or barium enema has not been supported by randomized
controlled trials. Consequently, the USPSTF and CTFPHC do not recommend for
or against colonoscopy, and USPSTF does not recommend for or against barium
enema in asymptomatic individuals at average risk of colorectal cancer.
CTFPHC did not consider screening with barium enema because of the lack of
direct evidence. The AGA concluded total colon examination (TCE) by
colonoscopy or barium enema were supported by indirect evidence, including
the panel’s decision analysis conducted to investigate the clinical
consequences of screening over time, despite the absence of direct evidence.
ACS also cites compelling indirect evidence for benefit and efficacy of TCE.
Consequently, the AGA, ACS and ICSI concluded that TCE by colonoscopy or
barium enema is an acceptable screening option.
Areas of Differences
Although all the organizations share the fundamental recommendation for
screening asymptomatic adults at average risk of colorectal cancer, there
are subtle differences in what they propose as optimal screening measures. A
difference between the ACS and the other groups concerns the recommendations
for FOBT and sigmoidoscopy. Although ACS and the other groups recommend
annual FOBT or flexible sigmoidoscopy every five years as acceptable
screening options, ACS notes that annual FOBT accompanied by flexible
sigmoidoscopy (every five years) is preferable to utilization of either test
alone. AGA and ICSI also recommend the combination of FOBT and flexible
sigmoidoscopy as a screening option; however, ACS is the only organization
to advocate the combination strategy as the preferred approach (over either
test alone). USPSTF and CTFPHC concluded there is insufficient evidence to
determine whether this combination of tests produces greater benefits than
either test alone.
Although all of the groups recommend screening with FOBT, CTFPHC is the only
group that does not specifically recommend annual testing. However, they
support screening in the periodic health examination of asymptomatic
patients over age 50 with no other risk factors.
Screening recommendations for people with a family history of colorectal
cancer vary among guidelines. AGA, USPSTF, ACS, and ICSI recommend increased
surveillance or earlier screening for these individuals. In contrast, CTFPHC
recommends that people with a family history of colorectal cancer or polyps
undergo the same screening as average risk individuals, stating insufficient
evidence to recommend colonsocopy for these individuals, unless the criteria
for hereditary non-polyposis colon cancer is met. Although CTFPHC
acknowledges that there is evidence of an increased prevalence of neoplasms
in these individuals, there is insufficient information to recommend more
intense screening than that of individuals at average risk.
Although there is general agreement among AGA, ACS, and CTFPHC regarding the
need for genetic counseling in individuals at risk for familial adenomatous
polyposis, CTFPHC is the only guideline to firmly recommend genetic testing.
The Task Force for the CTFPHC recommends genetic testing of individuals at
risk for familial adenematous polyposis if the genetic mutation has been
identified in the family and if genetic testing is available. This
recommendation is based on fair evidence to support the recommendation that
the manoeuvre be specifically considered in a periodic health examination.
USPSTF and ICSI do not comment on genetic counseling/screening as it is
beyond the scope of their guidelines.
Updates in Progress: A third USPSTF was appointed in September 1998 by the
Agency for Health Care Policy and Research (now known as the Agency for
Healthcare Research and Quality [AHRQ]). USPSTF recommendations from the 2nd
edition will be updated on an individual basis and new topics evaluated.
Reviews and recommendations will be released as they are completed. This
particular USPSTF guideline is currently under revision and is scheduled for
release in 2002.
Edward E. Rylander, M.D.
Diplomat American Board of Family Practice.
Diplomat American Board of Palliative Medicine.