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Screening

 Reviewed 05 Sept 2012

For the ‘average-risk’ population:

  • Average risk individuals are those with no additional personal or familial risk factors for colorectal cancer, other than age greater than 50 years.
  • Several randomized studies have shown significant reduction in mortality from colorectal cancer in persons over 50 years of age who were screened by fecal occult blood testing (FOBT).
  • Other accepted modalities include fecal immunochemical testing (FIT), flexible sigmoidoscopy (with or without FOBT) and colonoscopy.
  • Modalities such as computed tomography colonography, and fecal DNA, are not consistently accepted as screening tools at this time.
  • Patient preference and resource availability should guide selection of a single screening method, but the best evidence recommends that FOBT of asymptomatic individuals between age 50 and 75 be performed every one or two years.
  • Positive tests on FOBT, FIT and flexible sigmoidoscopy should be followed by evaluation of the entire colon with colonoscopy.
  • If available, screening should be conducted within an organized program incorporating quality assurance and equitable access rather than opportunistic screening.
  • Recommendations for routine screening in British Columbia have been developed and approved by MSP (see BCGuidelines.ca - Gastrointestinal System).
  • Additional information regarding the provincial colorectal cancer screening initiative is available on the BC Cancer Colon Screening Program website.

Inflammatory Bowel Disease

  • Risk of colorectal cancer in IBD depends on IBD-related factors such as disease extent, disease duration, dysplasia, concomitant primary sclerosing cholangitis, and non-IBD factors including family history of colorectal cancer.
  • Specific recommendations regarding frequency and type of screening is generally as per the treating gastroenterologist.

Hereditary/Genetic Syndromes

  • Approximately 10% of patients with colorectal cancer display a hereditary pattern.
  • Persons with one or more first-degree relatives diagnosed with colon or rectal cancer should consider screening at age 40 with colonoscopy.
  • Lynch Syndrome (or Hereditary nonpolyposis colorectal cancer (HNPCC)) due to germline mutations in mismatch repair genes accounts for 1-3% of all colorectal cancers, and displays an autosomal dominant pattern of inheritance although with smaller family sizes and fractured families, this classic pattern may not be apparent in the family history. Germline mutations of the mismatch repair genes result in a lifetime risk of colorectal cancer between 40-90%, earlier presentation of colorectal cancer (compared to sporadic), and increased risk for other extra-colonic malignancy. Screening of colon and other tumours by immunohistochemistry for the expression of mismatch repair proteins can indicate which tumours have evidence of mismatch repair deficiency; these people can then be referred to the Hereditary Cancer Program for further testing, including germline mismatch repair mutation screening if appropriate (see BC Cancer Hereditary Cancer Program (HCP)). Individuals with Lynch Syndrome  should be enrolled in a surveillance program of annual colonoscopy beginning at 20-25 years of age. Extra-colonic cancer screening is also recommended for some of the other Lynch Syndrome-associated cancers.
  • Familial adenomatous polyposis (FAP, including Gardner Syndrome) is responsible for 1% of colorectal cancer presentations, and is secondary to mutations of the adenomatous polyposis coli (APC) gene. Inherited in an autosomal dominant pattern, individuals develop 100-1000 adenomatous colonic polyps by the second to third decade of life, with a 90% risk of progressing to colorectal cancer. Diagnosis is established by genetic testing. Individuals at risk (carriers or indeterminate relatives) are recommended to have yearly flexible sigmoidoscopy beginning at puberty. Once polyposis is identified, colectomy should be performed, as the risk then rises to 100%. If there is rectal sparing, a subtotal colectomy with ileorectal anastomosis can be performed. If not, a total proctocolectomy with ileal pouch-anal anastomosis or end ileostomy should be performed. Gastric and duodenal polyps and ampullary cancer are at increased risk of development, and should be screened for with esophagogastroduodenoscopy and biopsy.
  • Relatives of individuals with genetically confirmed mutations should also be tested.
  • Please refer to the BC Cancer Hereditary Cancer Program (HCP) for description and indications for referral to HCP regarding: 
    • Hereditary Colorectal Cancer 
    • Familial Adenomatous Polyposis and other polyposis syndrome


SOURCE: Screening ( )
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