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    Colorectal Cancer Screening (PDQ®): Screening - Health Professional Information [NCI] - 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.
    Screening Intervention Study Design Internal Validity Consistency Magnitude of Effects External Validity
    Fecal Occult Blood Test RCTs Good Good 15%-33% Fair
    Sigmoidoscopy Case-control studies,[1]RCTs in progress Fair Fair About 60%-70% for left colon Fair
    Digital Rectal Exam Case-control studies Fair Good No effect Poor
    Colonoscopy Case-control studies, RCTs in progress Poor Poor About 60%-70% for left colon; uncertain for right colon Fair
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