HOME HELP CONTACT US FEEDBACK SUBSCRIPTIONS CURRENT ISSUE PAST ISSUES SEARCH		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Rapid Responses: Submit a response Alert me when this article is cited Alert me when Rapid Responses are posted Alert me if a correction is posted Services Email this article to a friend Related articles in CFP Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pineau, G. Search for Related Content PubMed PubMed Citation Articles by Pineau, G.

Should Canadians be offered systematic screening for colorectal cancer?

YES

Correspondence to: Dr Gilles Pineau, 453 Wiseman, Outremont, QC H2V 3J9; telephone 514 272-3800; e-mail gpineau{at}bellnet.ca

In 2007 in Canada, 20 800 people learned they had colorectal cancer—9400 women and 11 400 men. During the same year, 8700 died of this cancer—4000 women and 4700 men. In Canada over the past 25 years, the mean incidence of colorectal cancer has been stable and the mean mortality rate has shown a slight decrease. After lung cancer, colorectal cancer is the second leading cause of death by cancer in Canada. It is also the third most frequently diagnosed type of cancer in both women and men.¹

Most colon cancers start as an adenomatous polyp whose cells develop into cancer over a period of several years through a process that is not clearly understood. Surgical excision is the standard therapeutic approach; depending on the scope of the lesion, it might be accompanied by chemotherapy or radiation therapy. The prognosis is a direct function of the stage of the cancer.

In Canada, the survival rate at 5 years is 60% for colorectal cancer. More specifically, the survival rate at 5 years is higher than 90% for those with early-stage lesions (T1N0M0—stage 1 tumour, 0 nodes involved, and 0 metastases) and 5% for those with later-stage lesions (TxNxM1). It is of the utmost importance, therefore, to act as quickly as possible before the cancer spreads through the serous membrane and invades the lymph nodes.^2,3

Features of an effective screening program

The goal with screening is to detect cancerous or pre-cancerous lesions before there are symptoms. Screening can be incorporated into an organized program when the following conditions are met.^4,5

• The screening test reduces mortality.
  
• The screening test makes it possible to detect disease at a preclinical stage.
  
• The screening test makes it possible to predict accurately whethera person has cancer (a high degree of sensitivity) ordoes not have cancer (a highdegree of specificity).
  
• The screening test is considered safe and does not expose people to unacceptable risks.
  
• If screening reveals a cancer, effective treatment is available at an affordable cost.
  

Application to colorectal cancer

Colorectal cancer screening meets these conditions. About 90% of cases of colorectal cancer are diagnosed in Canadians older than 50 years. I estimate that, if an organized colorectal cancer screening program were offered to a population of men and women between the ages of 50 and 74 years and 70% of this population took part, colorectal cancer–related mortality could be reduced by at least 17%. This screening would consist of a fecal occult blood test every 2 years and, when there are positive test results, either a barium enema or colonoscopy.^4,6–8

This approach can be compared with the approach to screening for breast cancer, which consists of mammography every 2 years followed by a biopsy if mammography raises the possibility of a malignant tumour. In the case of the fecal occult blood test, 1 positive test in 10 actually turns out to be cancer. In the case of breast cancer screening, 1 lesion in 18 detected on mammography is cancerous.

The fecal occult blood test is risk free; however, it causes unnecessary concern in 9 out of 10 people screened; a mammary lesion detected on mammography causes unnecessary concern in 17 out of 18 women screened. On the other hand, barium enema and colonoscopy carry certain risks and definitely cause discomfort. The advantage of being almost certain of being able to cure a patient with a cancerous lesion that is caught early in its development or of preventing benign polyps from developing into malignant lesions outweighs the risks of these procedures. These small lesions can be removed by colonoscopy or sigmoidoscopy before they become cancerous.

Conclusion

Currently in Canada, we do not have extensive experience with an organized colorectal cancer screening program. Recently, Ontario, Manitoba, and Alberta launched colorectal cancer screening initiatives. We will need to monitor the development of these experiments as well as new technological developments. The reduction in mortality from breast cancer and cervical cancer owing, in part, to women’s participation in early screening is encouraging us to take action. Cancer organizations, public health authorities, and medical professionals all need to work together.^2,9,10

CLOSING ARGUMENTS Colorectal cancer screening meets all the conditions for creation of an effective screening program. This program would make it possible to reduce mortality due to colorectal cancer, which is responsible for 8700 deaths each year in Canada, by at least 17%. Family physicians should support the creation of a structured screening program and encourage their patients to participate in it.

 

Footnotes

The parties in this debate will refute each other’s arguments in rebuttals to be published in an upcoming issue.

Competing interests

None declared

Cet article se trouve aussi en français à la page 508.

References

1. Canadian Cancer Society, National Cancer Institute of Canada. Canadian cancer statistics 2007. Toronto, ON: Canadian Cancer Society, National Cancer Institute of Canada; 2007.
2. Kasper DL, Harrison TR. Harrison’s principles of internal medicine. 16 ed. New York, NY: McGraw-Hill, Medical Publishing Division; 2005.
3. DeVita VT, Hellman S, Rosenberg SA. Cancer: principles & practice of oncology. 7 ed. London, Engl: Lippincott Williams & Wilkins; 2005.
4. Canadian Cancer Society, National Cancer Institute of Canada. Canadian cancer statistics 2006. Toronto, ON: Canadian Cancer Society, National Cancer Institute of Canada; 2006.
5. Pollock RE, Doroshow JH, Khayat D, Nakao A, O’Sullivan B, editors. UICC manual of clinical oncology. 8 ed. Hoboken, NJ: Wiley Liss; 2004.
6. Hardcastle JD, Chamberlain JO, Robinson MH, Moss SM, Amar SS, Balfour TW, et al. Randomised controlled trial of faecal occult blood screening for colorectal cancer. Lancet 1996;348:1472-7.[Medline]
7. Kronborg O, Fenger C, Olsen J, Jorgensen OD, Sondergaard O. Randomised study of screening for colorectal cancer with faecal-occult-blood test. Lancet 1996;348:1467-71.[Medline]
8. Mandel JS, Bond JH, Church TR, Snover DC, Bradley GM, Schuman LM, et al. Reducing mortality from colorectal cancer by screening for fecal occult blood. Minnesota Colon Cancer Control Study. N Engl J Med 1993;328(19):1365-71. Erratum in: N Engl J Med 1993;329(9):672.[Abstract/Free Full Text]
9. Singh H, Turner D, Xue L, Targownik LE, Bernstein CN. Risk of developing colorectal cancer following a negative colonoscopy examination: evidence for a 10-year interval between colonoscopies. JAMA 2006;295(20):2366-73.[Abstract/Free Full Text]
10. Mandel JS. Which colorectal cancer screening test is best? J Natl Cancer Inst 2007;99(19):1424-5. Epub 2007 Sept 25.[Free Full Text]

Related articles in CFP:

Devrait-on offrir aux Canadiens le dépistage systématique du cancer colorectal?: OUI

Gilles Pineau
CFP 2008 54: 508-510. [Full Text]  

This Article Full Text (PDF) Rapid Responses: Submit a response Alert me when this article is cited Alert me when Rapid Responses are posted Alert me if a correction is posted Services Email this article to a friend Related articles in CFP Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Pineau, G. Search for Related Content PubMed PubMed Citation Articles by Pineau, G.