Vol 54: april • aVril 2008 Canadian Family Physician•Le Médecin de famille canadien
505
Should Canadians be offered
systematic screening for colorectal cancer?
I
t has been 5 years since the committee struck by Health Canada to study the issue of a national colorectal cancer screening program filed its report.1 This committee recommended screening for colorectal cancer for all Canadians 50 to 74 years old. This rec- ommendation was endorsed by the Canadian Cancer Society and is printed, every spring, in its annual report.In 2007, the Ontario government incorporated colorec- tal cancer screening into its health policies. No doubt, the initiative taken by the Ontario government will soon weigh heavily on every jurisdiction in the coun- try. And yet, it is a wrong-headed policy that has been adopted for the wrong reasons. Its implementation will require resources that are already extremely scarce in far too many other health care sectors.
We should not be asking healthy Canadians to get screened for colorectal cancer once they reach the age of 50 for reasons that have to do with both the natural history of the disease and the limitations of the recom- mended screening test.
Absolute risk of mortality
In public health, it is never appropriate to launch a pro- gram to prevent early mortality due to a specific cause in segments of the population already affected by high mortality due to all sorts of causes. It is a consequence of aging that larger numbers of people will die from an increasing number of causes, which is to say that the contribution that a specific cause makes to general mortality quickly becomes negligible. In this context, focusing on prevention of mortality caused by a specific disease becomes futile, even when a validated test is available. That is the first problem with colorectal cancer screening. Even if this screening were applied correctly, it would have no effect on the absolute risk of dying.
This phenomenon was in fact noted by the researchers in Minnesota who were the first to determine that it was
possible to reduce mortality from colorectal cancer with the fecal occult blood test.
It is estimated that, in 2007, 72 700 Canadians died of cancer; of these, 8700 (12%) died from colorectal cancer.
About 86% of deaths from colorectal cancer occur in the seventh, eighth, and ninth decades of life (7450/8700).2 Mortality due to all other causes is also increasing steadily in all of these age groups such that even if screening for colorectal cancer were widely accepted by the population and applied meticulously, it would not be possible to obtain a measurable reduction in the abso- lute risk of dying. Because this is an absurd eventual- ity, the principles framing public health practices should prohibit us from organizing this screening.
Test limitations
It gets worse. Although the test recommended for this screening, the fecal occult blood test, is capable of reducing mortality from colorectal cancer by 30%, it is a bad test because of the high number of false-positive results it produces. Think of the suffering that all these false-positive results create in a population for whom the mere possibility of cancer is a tragedy in and of itself. Some health professionals have taken heart from the fact that methods of validating positive results have become more reliable and more widely available. But this seems to me to be a rationalization after the fact.
The methods for confirming a diagnosis are neither pleasant nor completely safe. The National Committee estimates that, during the first 10 years of a widely used screening program, these methods will cause 75 deaths and 611 perforations.1 This is an exorbitant price to pay for a reduction in general mortality so minuscule that it cannot be measured.
Appropriate use of resources
And what of the considerable increase in the use of health services that such a program would no doubt
NO
Fernand Turcotte
MD MPH FRCPCThe parties in this debate will refute each other’s arguments in rebuttals to be published in an upcoming issue.
Debates
continued on page 506 Cet article se trouve aussi en français à la page 509.
506
Canadian Family Physician•Le Médecin de famille canadien Vol 54: april • aVril 2008cause? Given the bottlenecks that are already affect- ing too many health care sectors, how can we justify preparing for what could be a veritable tsunami of requests for gastroenterology services? And what of the work that will fall to family physicians in manag- ing the follow-up from this screening, which will be weighted toward the very great majority of those who receive positive test results? It is truly unfortunate that all the energy that family physicians will devote to supporting these patients, whom they have sent on ill-fated diagnostic journeys, will result in painful experiences that will probably ruin the quality of life of a substantial portion of their patients’ remaining days.
Dr Turcotte is a Professor Emeritus of Public Health in the Department of Social and Preventive Medicine in the Faculty of Medicine at Laval University in Quebec.
Competing interests None declared
Correspondence to: Dr Fernand Turcotte, Laval University, Department of Social and Preventive Medicine, 2180 Ste-Foy, Quebec, QC G1K 7P4; telephone
418 656-2131, extension 5975; fax 418 656-7759;
e-mail [email protected] references
1. National Committee on Colorectal Cancer Screening. Technical report for the National Committee on Colorectal Cancer Screening. Ottawa, ON: Public Health Agency of Canada; 2002.
2. Canadian Cancer Society, National Cancer Institute of Canada. Canadian can- cer statistics 2007. Toronto, ON: Canadian Cancer Society, National Cancer Institute of Canada; 2007.
CLOSING ARGUMENTS
•
Colorectal cancer screening does not reduce the absolute risk of mortality.
•
The fecal occult blood test is not a good screening test; it produces too many false-positive results.
•
Verification of positive fecal occult blood test results requires painful procedures that are not risk free for too many patients who are already vulnerable because of their age.
Conclusion
Currently in Canada, we do not have extensive experi- ence with an organized colorectal cancer screening pro- gram. 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
Dr Pineau is Vice President of the Quebec Division of the Canadian Cancer Society.
Competing interests None declared
Correspondence to: Dr Gilles Pineau, 453 Wiseman, Outremont, QC H2V 3J9; telephone 514 272-3800; e-mail [email protected]
references
1. Canadian Cancer Society, National Cancer Institute of Canada. Canadian can- cer statistics 2007. Toronto, ON: Canadian Cancer Society, National Cancer Institute of Canada; 2007.
2. Kasper DL, Harrison TR. Harrison’s principles of internal medicine. 16th ed.
New York, NY: McGraw-Hill, Medical Publishing Division; 2005.
3. DeVita VT, Hellman S, Rosenberg SA. Cancer: principles & practice of oncol- ogy. 7th ed. London, Engl: Lippincott Williams & Wilkins; 2005.
4. Canadian Cancer Society, National Cancer Institute of Canada. Canadian can- cer 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. 8th 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.
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.
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.
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.
10. Mandel JS. Which colorectal cancer screening test is best? J Natl Cancer Inst 2007;99(19):1424-5. Epub 2007 Sept 25.
CLOSING ARGUMENTS
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Colorectal cancer screening meets all the conditions for creation of an effective screening program.
•
This program would make it possible to reduce mor- tality due to colorectal cancer, which is responsible for 8700 deaths each year in Canada, by at least 17%.
•
