Please note: In 2003, the CTF updated its Grades of Recommendations to include an "I Recommendation" for situations where insufficient evidence exists to allow a recommendation to be made. (Formerly, these situations were captured under a "C Recommendation".) This change is not retroactive, and all "C Recommendations" made prior to 2003 have not been reevaluated in light of the new "I" recommendation grade. For a discussion of these recommendation grades, please link to the 2003 article in the Canadian Medical Association Journal here.
Preventive Health Care, 2001 Update: Colorectal Cancer Screening
Prepared by R. McLeod, MD, FRCSC, FACS, with the Canadian Task Force on Preventive Health Care
These recommendations were finalized by the Task Force in January 2000.
Contents
ObjectiveTo make recommendations on the effectiveness of specific screening techniques for colorectal cancer in asymptomatic patients. Effectiveness of screening in normal risk patients was reviewed for 1) multiphase screening with the Hemoccult test as first phase; 2) multiphase screening with sigmoidoscopy; 3) uniphase screening with colonoscopy. For above average risk patients, the specific screening maneuvers reviewed were: 1) flexible sigmoidoscopy and genetic testing for those with familial adenomatous polyposis (FAP); 2) colonoscopy for hereditary nonpolyposis colon cancer (HNPCC); and 3) colonoscopy for patients with family history (1st degree relative(s)) of polyps/colorectal cancer. This updates the 1994 review by the Canadian Task Force.
People with ulcerative colitis and
those who have had previous polyps or cancers have been excluded from this
review since the management of those with identifiable disease is not generally
part of the scope of a CTF review.
Burden
of SufferingColorectal
cancer is a leading cause of death in the western world.
In Canada, it was estimated that there would be 17,000 new cases of and
6,500 deaths from colorectal cancer in 2000.
Overall, colorectal cancer is the third most common cancer in Canada,
accounting for more than 12% of cases of cancer in both sexes. These rates,
particularly among men, are among the highest in the world.
Surgical resection remains the standard therapy for colorectal cancer but
adjuvant therapy with radiation and chemotherapy can improve the outcome in some
patients.
The etiology of colorectal cancer is unknown but most cancers arise from benign adenomas following the "polyp-cancer sequence". Most cancers occur sporadically but up to 15% of cancers may have a genetic basis. Thus, people with familial adenomatous polyposis, ( 1% of all colorectal cancers) and those with hereditary nonpolyposis colon cancer (HNPCC), which may account for another 5%, are at high risk for the development of colorectal cancer. Age is a significant risk factor. Less than 2% of cases occur in people under 40 years of age. The risk of colorectal cancer in a patient 50 years of age is 18 to 20 times that in a patient 30 years of age, and the risk doubles about every 7 years thereafter.
OptionsThe following maneuvers were considered: multiphase screening that begins with testing for fecal occult blood or sigmoidoscopy, uniphase screening with colonoscopy, and genetic testing. The appropriate intervals for screening and the procedures to be used for patients with selected risk factors also were evaluated. Screening with digital rectal examination and double contrast barium enema were not considered because of the lack of direct evidence.
OutcomesRates of cancer detection, deaths from colorectal cancer, compliance, feasibility and accuracy of each manoeuver were considered.
EvidenceMEDLINE was searched for English language articles published between January 1966 and January 2001 using the MESH terms "screening" and "colorectal neoplasia." The reference sections of review articles were used to cross-reference the MEDLINE search and content experts were canvassed to ensure that no relevant articles were missed. Articles concerning Hemoccult testing or flexible sigmoidoscopy, as the first step in a multiphase secondary prevention strategy, or colonoscopy, as a single-phase secondary prevention strategy in both asymptomatic and high-risk groups, were included.
Recommendations were graded as:
| Good evidence to support the recommendation that the condition be specifically considered in a PHE. | |
| Fair evidence to support the recommendation that the condition be specifically considered in a PHE. | |
| Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds. | |
| Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE. | |
| Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE. |
Quality of evidence was rated according to 5 levels:
| Evidence from at least 1 properly randomized controlled trial (RCT). | |
| Evidence from well-designed controlled trials without randomization. | |
| Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group. | |
| Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here. | |
| Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees. |
ValuesThe 9 member Task Force of experts in family medicine, geriatric medicine, paediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness. Patient preferences were not discussed. The lead author prepared a manuscript providing critical appraisal of the evidence. This included identification and critical appraisal of key studies, and ratings of the quality of this evidence using the Task Force's established methodological hierarchy. The resulting summary of proposed conclusions and recommendations for consideration was presented and deliberated upon at 3 Task Force Meetings in January and June of 1999 and January 2000.
Benefits,
Harms, and CostsHemmocult testing
There is evidence from RCTs that fecal occult blood testing results in a significant decrease in mortality from colorectal cancer, but not in overall mortality. The relative risk reduction is approximately 15% and in absolute terms, approximately 8.5 deaths from colorectal cancer would be averted if 10,000 people were screened over 10 years. The sensitivity of the test was approximately 50% in 3 of the trials and concern remains about the sensitivity of Hemoccult testing and the potential for false reassurance. The psychological issues of screening and the acceptability of screening on a community basis have not been studied. Compliance rates have varied for both initial testing and follow-up investigations
Sigmoidoscopy
There is evidence from case control
studies that sigmoidoscopy may reduce the risk of death from colorectal cancer.
RCT evidence suggests that flexible sigmoidoscopy may be superior in
detecting adenomas and possibly cancer than FOBT.
However, the trials are small and do not report mortality data.
Therefore, the benefit of flexible sigmoidoscopy alone compared with FOBT or in
combination with FOBT cannot be ascertained. However, there is fair evidence to
suggest that sigmoidoscopy may reduce mortality from colorectal cancer. Flexible
sigmoidoscopy may be preferable to rigid sigmoidoscopy, because the physician
can examine the more proximal colon with the flexible sigmoidoscope than with
the rigid one and thus detect more adenomas and carcinomas.
The flexible sigmoidoscope may be more acceptable to patients and safer.
Bowel perforations occur at a rate of 1.4 per 10,000 flexible
sigmoidoscopic examinations of asymptomatic patients. It does require a more
qualified examiner than rigid sigmoidoscopy
Colonoscopy
There is no direct evidence about the
effectiveness of colonoscopy as a screening manoeuver in asymptomatic, average
risk individuals. Perforation rates are higher with colonoscopy than
sigmoidoscopy, (approx. 10 per 10,000 procedures). Since approximately 45% of
cancers are right sided in HNPCC families, colonoscopy is the preferred method
of screening
RecommendationsRecommendation
grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III]
are indicated after each recommendation. Citations in support of individual
recommendations are identified in the guideline text.
Average Risk Individuals
Screening with the Hemoccult test: 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 RCTs found no improvement in positivity rates or change in compliance rates with moderate dietary restrictions.
Screening with sigmoidoscopy: 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]. There is insufficient evidence to make recommendations about whether only 1 or both of FOBT and sigmoidoscopy should be performed [C, I].
Screening
with colonoscopy:
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.
Above Average Risk Individuals
Individuals at Risk for Familial Adenomatous Polyposis (FAP): The Task Force recommends genetic testing of individuals at risk for FAP 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.
Individuals
at Risk for Hereditary Non-Polyposis Colon Cancer (HNPCC)
Individuals with a Family History of Polyps or Colon Cancer: 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 HNPCC [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.
Because
most screening options are multiphasic, it is preferable that there is
adequate infrastructure to support the implementation, assure quality
control and the timely follow-up of screened individuals.
ValidationThe task force and lead author arrived at the final decisions on recommendations unanimously. After CTF consensus was reached, 4 experts in the field reviewed the manuscript and their suggestions were incorporated as needed.
Sponsors Selected
ReferencesR. McLeod with the Canadian Task Force on Preventive Health Care. Screening Strategies for Colorectal Cancer: Systematic Review & Recommendations. CTFPHC Technical Report #01-2. February, 2001. London, ON: Canadian Task Force.
Link to Published Recommendation Statement
Link to Full Technical Report (in pdf)
Link to Summary Table of Recommendations of this review
Link to Selected References list of this review
Link to 1994 Chapter: Screening for Colorectal Cancer
Copyright © 2000 Canadian
Task Force on Preventive Health Care
For any technical issues please contact: webmaster@ctfphc.org
Last modified: August 05, 2003
