Summary of Evidence

Note: Separate PDQ summaries on Colorectal Cancer Prevention; Colon Cancer Treatment; and Rectal Cancer Treatment are also available.

Based on solid evidence, screening for colorectal cancer (CRC) reduces CRC mortality, but there is little evidence that it reduces all-cause mortality, possibly because of an observed increase in other causes of death.

Table 1. Effect of Screening Intervention on Reducing Mortality from Colorectal Cancer
table 1. Effect of Screening Intervention on Reducing Mortality from Colorectal Cancer<SUP>a</SUP>
Screening Intervention Study DesignInternal ValidityConsistencyMagnitude of EffectsExternal Validity
RCT = randomized controlled trial.
aThere are no data on the effect of other screening interventions (i.e., fecal occult blood test combined with sigmoidoscopy, barium enema, colonoscopy, computed tomographic colonography, and stool DNA mutation tests) on mortality from colorectal cancer.
Fecal Occult Blood Test RCTs GoodGood15%–33%Fair
SigmoidoscopyCase-control studies[1], RCTs in progressFairFairAbout 60%–70% for left colonFair
Digital Rectal ExamCase-control studiesFairGoodNo effectPoor
ColonoscopyCase-control studies, RCTs in progressPoorPoorAbout 60%–70% for left colon; uncertain for right colonFair

Table 2. Effect of Screening Intervention on Surrogate Endpoints (e.g., Stage at Diagnosis and Adenoma Detection)
table 2. Effect of Screening Intervention on Surrogate Endpoints (e.g., Stage at Diagnosis and Adenoma Detection)
Screening InterventionStudy DesignInternal ValidityConsistencyMagnitude of Effects on Surrogate EndpointsExternal Validity
CRC = colorectal cancer; CT = computed tomography; FOBT = fecal occult blood test; iFOBT = immunochemical fecal occult blood test; N/A = not available.
Sigmoidoscopy [2] [3]Case-control studies PoorFairAbout 45% decrease in detection rate of cancers compared with colonoscopyPoor
FOBT/ Sigmoidoscopy [4][5]Randomized controlled studiesFairPoorNo difference in diagnostic yield between sigmoidoscopy + FOBT vs. sigmoidoscopy aloneN/A
Barium Enema [6]Ecologic and descriptive studiesFairPoorBarium enema detects about 30%–50% of cancers detected by colonoscopyN/A
Colonoscopy [7][8]Ecologic and descriptive studiesFairPoorAbout 3% of patients with no distal adenomas have advanced proximal neoplasia. There is a threefold increase in this rate in patients with distal adenomas.N/A
CT Colonography [9] [10][11]Ecologic and descriptive studiesFairPoorCT colonography may have similar sensitivity to colonoscopy in certain centersPoor
Stool DNA Mutation Tests [12]Studies in progress UnknownUnknownUnknownUnknown
Immunochemical FOBTCross-sectional study in which iFOBT is administered to persons receiving colonoscopy GoodGoodiFOBT detects >60% and ≤90% of CRCsN/A


1. Thiis-Evensen E, Hoff GS, Sauar J, et al.: Population-based surveillance by colonoscopy: effect on the incidence of colorectal cancer. Telemark Polyp Study I. Scand J Gastroenterol 34 (4): 414-20, 1999.[PUBMED Abstract]

2. Cotterchio M, Manno M, Klar N, et al.: Colorectal screening is associated with reduced colorectal cancer risk: a case-control study within the population-based Ontario Familial Colorectal Cancer Registry. Cancer Causes Control 16 (7): 865-75, 2005.[PUBMED Abstract]

3. Schoenfeld P, Cash B, Flood A, et al.: Colonoscopic screening of average-risk women for colorectal neoplasia. N Engl J Med 352 (20): 2061-8, 2005.[PUBMED Abstract]

4. Segnan N, Senore C, Andreoni B, et al.: Randomized trial of different screening strategies for colorectal cancer: patient response and detection rates. J Natl Cancer Inst 97 (5): 347-57, 2005.[PUBMED Abstract]

5. Gondal G, Grotmol T, Hofstad B, et al.: The Norwegian Colorectal Cancer Prevention (NORCCAP) screening study: baseline findings and implementations for clinical work-up in age groups 50-64 years. Scand J Gastroenterol 38 (6): 635-42, 2003.[PUBMED Abstract]

6. Winawer SJ, Stewart ET, Zauber AG, et al.: A comparison of colonoscopy and double-contrast barium enema for surveillance after polypectomy. National Polyp Study Work Group. N Engl J Med 342 (24): 1766-72, 2000.[PUBMED Abstract]

7. Lieberman DA, Weiss DG, Bond JH, et al.: Use of colonoscopy to screen asymptomatic adults for colorectal cancer. Veterans Affairs Cooperative Study Group 380. N Engl J Med 343 (3): 162-8, 2000.[PUBMED Abstract]

8. Imperiale TF, Wagner DR, Lin CY, et al.: Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings. N Engl J Med 343 (3): 169-74, 2000.[PUBMED Abstract]

9. Pickhardt PJ, Choi JR, Hwang I, et al.: Computed tomographic virtual colonoscopy to screen for colorectal neoplasia in asymptomatic adults. N Engl J Med 349 (23): 2191-200, 2003.[PUBMED Abstract]

10. Cotton PB, Durkalski VL, Pineau BC, et al.: Computed tomographic colonography (virtual colonoscopy): a multicenter comparison with standard colonoscopy for detection of colorectal neoplasia. JAMA 291 (14): 1713-9, 2004.[PUBMED Abstract]

11. Mulhall BP, Veerappan GR, Jackson JL: Meta-analysis: computed tomographic colonography. Ann Intern Med 142 (8): 635-50, 2005.[PUBMED Abstract]

12. Imperiale TF, Ransohoff DF, Itzkowitz SH, et al.: Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population. N Engl J Med 351 (26): 2704-14, 2004.[PUBMED Abstract]

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