Colorectal Screening for Cancer Prevention in Asymptomatic Patients

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Effective Date: March 1, 2013
Revised Date: June 22, 2016

Recommendations and Topics


This guideline provides recommendations for the detection of colorectal cancer and adenomas in asymptomatic patients, aged >19 years. It does not apply to patients with previous colorectal adenomas or cancer, anemia, or bowel related symptoms. Any symptoms need to be investigated promptly. Recommendations following removal of colorectal adenomas or cancer can be found at - Follow-up of Colorectal Polyps or Cancer.


Key Recommendations

  • Screening for colorectal cancer should occur after risk stratification which determines the appropriate screening test and interval.
  • Fecal immunochemical test (FIT) every 2 years for average-risk individuals aged 50 - 74 years.*
  • Follow-up of ANY positive fecal occult blood test (FOBT) with colonoscopy.
  • Use of FOBT is not appropriate when frank blood is present.
  • Colonoscopy every 10 years is an acceptable alternative to FOBT for screening.
  • Patients followed by colonoscopy do not require other screening modalities (i.e., FOBT).

* This has been revised from 1-2 years (March 2013) to 2 years (June 2016).



Colorectal cancer (CRC) ranks as the third most common malignancy in Canada and the second most frequent cause of cancer death. 1 The incidence of CRC rises steadily after the age of 50. More than 1100 people die each year from CRC in British Columbia (BC).1 The age-standardized incidence rate of CRC in BC in 2012 was 53/100,000 men and 35/100,000 women.1

Table 1: Lifetime Probability of Developing or Dying from Colorectal Cancer in BC.1


Lifetime Probability

Probability (%) of Developing Cancer in Next 10 Years by Age


Developing CRC %

Dying CRC

























In patients who are 50 years and older, more than 25% will have at least one adenoma. The majority of CRCs arise from pre-existing adenomas, the 'adenoma-carcinoma sequence'. Two major types of polyps are found in the colon and rectum: adenomas and hyperplastic polyps. Hyperplastic polyps are considered to have no malignant potential.

The risk of an adenoma becoming malignant is greatest for "advanced" adenomas:

  • tubular adenomas ≥ 1 cm,
  • villous adenomas,
  • adenoma with high grade dysplasia (HGD),
  • sessile serrated polyps ≥ 1 cm,
  • sessile serrated polyps with dysplasia,
  • or traditional serrated adenoma.

Individuals with multiple adenomas of any size are also at increased risk.2 Because it generally takes 5-10 years for a small adenoma to develop into a malignancy, cancer may be prevented by adenoma removal.3


Risk Factors

The most important risk factor for CRC is age over 50.3,4

Additional risk factors for CRC include:2,4

  • Personal history of adenoma(s)
  • Family history
  • Long standing (at least 8 years) inflammatory bowel disease involving the colon

Approximately 75% of all CRC occurs in patients of average risk with no family history.4 In general, having a single affected second degree relative with CRC does not significantly increase one's risk of CRC. At the present time there is no evidence that people with other sporadic cancers (e.g., breast, prostate) are at increased risk of developing CRC.

Other risk factors for CRC may include diet, smoking, sedentary lifestyle and obesity. These risk factors are newly recognized but there is currently insufficient evidence to modify screening recommendations.

*1st degree relatives have a blood relationship to the patient: parents, brothers, sisters and children. 
2nd degree relatives have a blood relationship to the patient: aunts, uncles, nieces, nephews, grandparents and grandchildren.


Indications for Screening

Individuals who are asymptomatic can be classified as having average or increased risk for CRC:

Average risk patients:

  • Meet none of the criteria below for increased risk

Increased risk patients:

  • Personal history of adenomas, particularly advanced or multiple adenomas - see - Follow-up of Colorectal Polyps or Cancer
  • 1st degree relative age < 60 with CRC or advanced or multiple adenomas - see Appendix A
  • Two or more 1st degree relatives with CRC at any age
  • Longstanding inflammatory bowel disease2
  • Family history of familial FAP or HNPCC - see Appendix A: Factors Influencing Colorectal Cancer Risk (PDF, 121KB)



Average Risk Asymptomatic Patients, aged 50 to 74 years6

Fecal immunochemical test (FIT) every 2 years is recommended* (see Table 2),7,8 with any positive FIT to be followed by a colonoscopy. There is direct evidence from several population-based prospective randomized trials that FOBT, with follow-up of any positive result with colonoscopy, can reduce mortality from CRC.8

A colonoscopy is also an acceptable screening option every 10 years. For an average risk individual with a negative colonoscopy, further screening of any type is not required for 10 years. After a 10 year interval, the choice of subsequent screening modality can be determined.

Average Risk Asymptomatic Patients, aged over 74 years

For patients over the age of 74 years, the value of screening should be individually assessed taking into account a balance of the risks, benefits and patient comorbidities. Screening is not recommended after 85 years of age.13

Increased Risk Asymptomatic Patients, of any age5

With single 1st degree relative younger than age 60 with CRC or advanced adenoma(s) or two or more 1st degree relatives of any age with CRC, the recommended screening is:

  • Colonoscopy every 5 years starting at age 40, or 10 years earlier than the age of youngest affected relative at diagnosis.
  • Use FOBT, FS and CT colonography only when patients decline colonoscopy or have an incomplete colonoscopy.

With inflammatory bowel disease involving the majority of the colon for over 8 years or the left colon for over 15 years,14 the recommended screening is:

  • Colonoscopy every 1 to 2 years with multiple biopsies to detect occult neoplasia (dysplasia).

For information on increased risk due to family history of FAP or HNPCC, see Appendix A: Factors Influencing Colorectal Cancer Risk (PDF, 121KB).

Surveillance of Patients with Prior History

The following patients should undergo a surveillance program as outlined in - Follow-up of Colorectal Polyps or Cancer:

  • Personal history of CRC
  • Personal history of an advanced adenoma (see definition above)
  • Personal history of 1 or 2 non-advanced adenomas

* This has been revised from 1-2 years (March 2013) to 2 years (June 2016).

Controversies in Care

Other methods for CRC screening are available. There is no single infallible technique for detection, but an effective screening technique for CRC should be feasible, accurate, safe, acceptable, and cost-effective.

  • Flexible sigmoidoscopy (FS) has been used as a once only screening tool in the UK for individuals 55 - 64 years.9 The prevalence of adenomas in the proximal colon markedly increases with age, while prevalence of adenomas in the rectum and sigmoid colon plateau after age 59 years.10 This can limit the utility of FS.
  • CT colonography every 5 years from age 50 has been recommended in some US guidelines11 but other guidelines, including those from Canadian Association of Gastroenterology, do not recommend a CT colonography for average risk screening. 12,13


Test Options

The following are test options that are available for screening and diagnosis. Pros and cons for each test are listed as well as the tests that are no longer recommended. For patients who test positive on any non-colonoscopy screeningtest, a full colonoscopy is advised.

Fecal Occult Blood Test (FOBT)

As discussed above in Screening, FOBT (FIT preferred) is a cost effective method15 and the most convenient first line screening modality in BC. Any positive test should be investigated with a colonoscopy. Patients undergoing regular colonoscopic screening do not require FOBT. It is recommended that patients who report frank blood in the stool not have FOBT but instead be referred for possible endoscopic investigation. Digitally obtained stool should not be used for FOBT; testing is performed on spontaneously evacuated stool.16 FIT is preferable to guaiac FOBT (Table 2). 17

Pro: non-invasive; inexpensive; widely available.
Con: lower sensitivity and specificity than direct visualization for neoplasia; variable patient compliance; frequency of testing.

Table 2: Test Performance of gFOBT Versus FIT (>100 ng/mL)




Interaction with diet or medications



PPV† for all advanced adenomas and cancer



NPV‡ for all advanced adenomas and cancer



Specificity for human hemoglobin

Yes - antibody directed against human globin

No - reacts with any source of heme

Patient Participation



* Auto-OC Micro
** Hemoccult II
† Positive predictive value (PPV) - The percentage of patients with a positive test who actually have the disease.
‡ Negative predictive value (NPV) - The percentage of patients with a negative test who do not have the disease.


Colonoscopy is the gold standard for adenoma detection and removal to prevent CRC.2,3,23 Colonoscopy allows for direct inspection of the entire colon, and allows for biopsy and polypectomy. It requires a thorough bowel preparation. Complications can arise from the bowel preparation as well as the procedure.

Pro: high sensitivity and specificity; allows for immediate biopsy and polypectomy; examines entire colon; longer interval between screening.

Con: usually requires sedation to minimize discomfort; risk of serious complications (perforations 3.8 per 10,000);13,22accuracy and complication rate of the colonoscopy depends on the expertise of the endoscopist and adequacy of preparation; access and cost.

Flexible Sigmoidoscopy

Flexible sigmoidoscopy examines the rectum and sigmoid colon. It can usually be done without sedation but does require some colon preparation.9

Pro: usually does not require sedation; allows for immediate biopsy and polypectomy; has random controlled trial evidence for reduction of CRC incidence and mortality.9

Con: proximal colon is not examined;20 discomfort; accuracy and complication rate of the sigmoidoscopy depends on the expertise of the endoscopist and adequacy of preparation; distal lesions require further full colonoscopy due to risk of proximal lesions; risk of complications (perforations 0.46 per 10,000).13

CT Colonoscopy

CT Colonography images the entire colon utilizing a CT scanner. It requires a thorough bowel preparation and insufflation of carbon dioxide gas through the rectum. This test also images extraluminal structures. Complications can arise from the bowel preparation.

Pro: minimally invasive; low complication rate (perforations 0.46 per 10,000) compared to colonoscopy;24 no sedation used; usually effective where colonoscopy is technically incomplete.

Con: discomfort; radiation exposure; high cost procedure; reduced sensitivity for detection of flat polyps and polyps <6 mm;25 does not permit biopsy or polyp removal; the accuracy depends on expertise of the radiologist and adequacy of preparation; there are currently no outcome studies regarding CRC mortality prevention.

Not Recommended for Screening

Evidence does not support the use of the following as screening tools for CRC in asymptomatic patients:

  • Digital Rectal Exams (DRE)
  • Barium enemas
  • Carcinoembryonic Antigen (CEA) tests
  • Combined use of FOBT with flexible sigmoidoscopy for primary screening




  1. Canadian Cancer Society's Steering Committee on Cancer Statistics. Canadian Cancer Statistics 2012. Toronto, ON: Canadian Cancer Society; 2012.
  2. ASGE Standards of Practice Committee. Colorectal cancer screening and surveillance. Gastrointest Endosc. 2006;63:546-558.
  3. Zauber AG, Winawer SJ, O'Brien MJ, et al., Colonoscopic polypectomy and long-term prevention of colorectal-cancer deaths. NEJM. 2012;366:687-696.
  4. Wilschut JA, Habbema JDF, Ramsey SD, et al., Increased risk of adenomas in individuals with a family history of colorectal cancer: results of a meta-analysis. Cancer Causes Control 2010;21:2287-93.
  5. Fuchs CS, Giovannucci EL, Colditz GA, et al., A prospective study of family history and the risk of colorectal cancer. N Engl J Med. 1994;331:1669-74.
  6. Qaseem A, Denberg TD, Hopkins RH, et al., Screening for colorectal cancer: a guidance statement from the American College of Physicians. Ann Intern Med. 2012;156:378-386.
  7. Mandel JS, Church TR, Bond JH, et al., The effect of fecal occult-blood screening on the incidence of colorectal cancer. N Engl J Med. 2000;343:1603-1607.
  8. Duffy MJ, van Rossum LGM, van Turenhout ST, et al., Use of faecal markers in screening for colorectal neoplasia: a European group on tumour markers position paper. Int J Cancer. 2011;128:3-11.
  9. Atkin W, Edwards R, Kralj-Hans I, et al., Once-only flexible sigmoidoscopy screening in prevention of colorectal cancer: a multicentre randomised controlled trial. Lancet 2010;375:1624-33.
  10. Segnan N, Senore C, Andreoni B, et al., Comparing attendance and detection rate of colonoscopy with sigmoidoscopy and FIT for colorectal cancer screening. Gastroenterology 2007;132(7):2304-2312.
  11. Levin B, Lieberman DA, McFarland B, et al., Screening and surveillance for the early detection of colorectal cancer and adenomatous polyps, 2008: A joint guideline from the American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American College of Radiology. Gastroenterology 2008;134:1570-1595.
  12. Leddin DJ, Enns R, Hilsden R, et al., Canadian Association of Gastroenterology position statement on screening individuals at average risk for developing colorectal cancer: 2010. Can J Gastroenterol. 2010;24:705-714.
  13. U.S. Preventive Services Task Force, Screening for Colorectal Cancer: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2008;149:627-637.
  14. Kornbluth A, Sachar DB, and The Practice Parameters Committee of the American College of Gastroenterology, Ulcerative colitis practice guidelines in adults. Am J Gastroenterol. 2010;105:500.
  15. Telford JJ, Levy AR, Sambrook JC, Zou D, Enns RA. The cost-effectiveness of screening for colorectal cancer. CMAJ 2010;182:1307-13.
  16. Collins JF, Lieberman DA, Durbin TE, Weiss DG. Accuracy of screening for fecal occult blood on a single stool sample obtained by digital rectal examination: a comparison with recommended sampling practice. Ann Intern Med. 2005;142:81-85.
  17. Hewitson P, Glasziou PP, Irwig L, Towler B, Watson E. Screening for colorectal cancer using the faecal occult blood test, Hemoccult. Cochrane Database of Systematic Reviews 2007, Issue 1. Art. No.: CD001216. DOI: 10.1002/14651858.CD001216.pub2
  18. Van Rossum L, Van Rijn A, Laheij R, et al., Random comparison of guaiac and immunochemical fecal occult blood tests for colorectal cancer in a screening population. Gastroenterology 2008;135:82-90.
  19. Levi Z, Rozen P, Hazazi R, et al., A quantative immunochemical fecal occult blood test for colorectal neoplasia. Ann Intern Med. 2007;146:244-255.
  20. 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. 2004;351:2704-2714.
  21. Lieberman DA, Weiss DG. One-time screening for colorectal cancer with combined fecal occult-blood testing and examination of the distal colon. N Engl J Med 2001; 345(8):555-560.
  22. Whitlock EP, Lin JS, Liles E, Beil TL, Fu R, O'Connor E, et al. Screening for colorectal cancer: an updated systematic review. Evidence Synthesis No. 65, Part 1. AHRQ publication no. 08-05124-EF-1. Rockville, MD: Agency for Healthcare Research and Quality; October 2008.
  23. Baxter NN, Goldwasser MA, Paszat LF, et al., Association of colonoscopy and death from colorectal cancer. Ann Intern Med. 2009;150:1-8.
  24. Pickard PJ, Incidence of colonic perforation at CT colonography: review of existing data and implications for screening of asymptomatic adults. Radiology 2006;239:313-16.
  25. Johnson CD, Chen MH, Toledano AY, et al., Accuracy of CT colonography for detection of large adenomas and cancers. N Engl J Med. 2008;359:1207-17.



Appendix A: Factors Influencing Colorectal Cancer Risk (PDF, 121KB)

Associated Documents

The following documents accompany this guideline:

This guideline is based on scientific evidence current as of the Effective Date.

This guideline was developed by the Guidelines and Protocols Advisory Committee, approved by the British Columbia Medical Association, and adopted by the Medical Services Commission.


The principles of the Guidelines and Protocols Advisory Committee are to:

  • encourage appropriate responses to common medical situations
  • recommend actions that are sufficient and efficient, neither excessive nor deficient
  • permit exceptions when justified by clinical circumstances.
Contact Information
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Victoria BC V8W 9P1
Web site:
Clinical Practice Guidelines


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