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 Cancera
RCT = randomized controlled trial.
a There 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 ||Sigmoidoscopy||Digital Rectal Exam ||Colonoscopy|
|Study Design||RCTs||Case-control studies , RCTs in progress||Case-control studies||Case-control studies, RCTs in progress|
|Magnitude of Effects||15%-33% ||About 60%-70% for left colon||No effect||About 60%-70% for left colon; uncertain for right colon|
Table 2. Effect of Screening Intervention on Surrogate Endpoints (e.g., Stage at Diagnosis and Adenoma Detection)
CRC = colorectal cancer; CT = computed tomography; FOBT = fecal occult blood test; iFOBT = immunochemical fecal occult blood test; N/A = not available.
|�||Sigmoidoscopy [2,3]||FOBT/ Sigmoidoscopy [4,5]||Barium Enema ||Colonoscopy [7,8]||CT Colonography [9,10,11]||Stool DNA Mutation Tests ||Immunochemical FOBT|
|Study Design||Case-control studies ||Randomized controlled studies||Ecologic and descriptive studies||Ecologic and descriptive studies||Ecologic and descriptive studies||Studies in progress||Cross-sectional study in which iFOBT is administered to persons receiving colonoscopy|
|Magnitude of Effects on Surrogate Endpoints||About 45% decrease in detection rate of cancers compared with colonoscopy||No difference in diagnostic yield between sigmoidoscopy + FOBT vs. sigmoidoscopy alone||Barium enema detects about 30%-50% of cancers detected by colonoscopy||About 3% of patients with no distal adenomas have advanced proximal neoplasia. There is a threefold increase in this rate in patients with distal adenomas.||CT colonography may have similar sensitivity to colonoscopy in certain centers ||Unknown||iFOBT detects >60% and ?90% of CRCs|
|External Validity||Poor||N/A ||N/A||N/A ||Poor||Unknown||N/A|
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- 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.