Rebuttal: Population-based fecal occult blood screening for colon cancer [CMAJ

Rebuttal
Drs. Winawer and Zauber respond to Dr. Marshall

CMAJ 2000;163(5):547 [See Dr. Marshall's rebuttal]

See also:

Screening for colorectal cancer C.J. Wright; G. Brock, V. Gurekas; P. Koduri [Letters]
eLetters

Kenneth Marshall uses misleading data, unfounded assumptions and exaggerations to support his bias against screening.¹ Calculating the number of people needed to be screened to save one life is misleading when it is used as the only measure of screening benefit. A more complete assessment of screening benefit is years of useful life gained. Using a computer simulation model of the clinical consequence of screening, we can estimate that 12 325 life-years would be saved per 100 000 people screened with fecal occult blood testing annually.² Death is inevitable, but premature death can be prevented. Death from colorectal cancer constitutes about 3% of the total mortality; therefore, the effect of colorectal cancer screening on total mortality cannot be demonstrated with the comparatively small sample size of clinical trials.

To say that screening distorts the communal value system is unfounded. What is preferable — a family focused on wellness, or family devastated by a lethal disease? Colorectal cancer screening is as cost-effective as mammography. There is also a cost of failure to screen, failure to detect early curable cancer, failure to prevent morbidity, and failure to find and remove screen-detected adenomatous polyps with the resultant decrease in incidence of colorectal cancer. These polyps are found by screening, not by random chance.² With rising medical costs and decreasing screening costs, screening is actually becoming cost-saving.^2,3,4,5

Marshall exaggerates possible screening harms. Psychological and medical harms have been studied and have not been demonstrated.^6,7 False reassurance with a program of annual fecal occult blood testing is uncommon; sensitivity for cancer with this approach is over 90%.⁸ Screening has been shown to have a net benefit in reducing colorectal cancer mortality.² Marshall's statement of a 7% mortality following surgical resection of polyps is inflated. Resection is rarely needed today, but in those rare instances when it is required it has demonstrated an excellent risk–benefit ratio.⁷

Dr. Marshall raises the specter of colonoscopy complication rates, which have fallen considerably and are now 1 to 2 per 1000 cases.² Complications from diagnostic colonoscopy are rare; almost all result from polypectomy, which is performed to prevent cancer. No cardiopulmonary deaths occurred after the 13 000 colonoscopies in the Minnesota trial.⁹ Only 2 cases of hepatitis C transmission have been reported,¹⁰ both of which involved improper disinfection of the instrument. The introduction of colonoscopy, its demonstrated safety after 30 years of experience, and standards for training, clinical application and disinfection of equipment now make screening feasible.¹¹

An estimated 2250 people in Ontario will die of colorectal cancer this year.⁵ Their families should not have to bear the loss. We now have screening techniques with acceptable sensitivity and specificity, accurate diagnostic methods and definitive treatment with colonoscopic polypectomy and cancer surgery. We can intervene and make a difference in their lives. Losing even one life prematurely is a tragedy.¹²

This article has been peer reviewed.

References

    1.    Marshall KG. Population-based fecal occult blood screening for colon cancer: Will the benefits outweigh the harm? CMAJ 2000;163(5):545-6.

    2.    Winawer SJ, Fletcher RH, Miller L, Godlee F, Stolar MH, Mulrow CD, et al. Colorectal cancer screening: clinical guidelines and rationale. Gastroenterology 1997;112:594-642. [MEDLINE]

    3.    Wagner JL, Tunis S, Brown M, Ching A, Almeida R. The cost-effectiveness of colorectal cancer screening in average-risk adults. In: Young G, Levin B, Rozen A, editors. Prevention and early detection of colorectal cancer. London: WB Saunders; 1996. p. 321-56.

    4.    Lieberman DA. Cost-effectiveness model for colon cancer screening. Gastroenterology 1995;109:1781-6. [MEDLINE]

    5.    Ontario Expert Panel on Colorectal Cancer Screening. Colorectal cancer in Ontario 1971–1996. Toronto: Cancer Care Ontario; 1999. Available: www.cancercare.on.ca/ocr/colorectal (accessed 2000 Aug 3).

    6.    Thiis-Evensen E, Wihelmsen I, Hoff GS, Blomhoff S, Sauar J. The psychological effect of attending a screening program for colorectal polyps. Scand J Gastroenterol 1999;34:103-9. [MEDLINE]

    7.    Robinson MHE, Hardcastle JD, Moss SM, Amar SS, Chamberlain JO, Armitage NCM, et al. The risks of screening: data from the Notingham randomised controlled trial of faecal occult blood screening for colorectal cancer. Gut 1999;45:588-92. [MEDLINE]

    8.    Church TR, Ederer F, Mandel JS. Fecal occult screening in the Minnesota Study: sensitivity of the screening test. J Natl Cancer Inst 1997;89:1440-8. [MEDLINE]

    9.    Mandel JS, Bond JH, Bradley M, Snover DC, Church TR, Williams S, et al. Sensitivity, specificity, and positive predictivity of the Hemoccult test in screening for colorectal cancers: The University of Minnesota's Colon Cancer Control Study. Gastroenterology 1989;97:597-600. [MEDLINE]

    10.    Bronowicki JP, Venard V, Botté C, Monhoven N, Gastin I, Chone L, et al. Patient-to-patient transmission of hepatitis C virus during colonoscopy. N Engl J Med 1997;337:237-40. [MEDLINE]

    11.    American Society for Gastrointestinal Endoscopy Technology Assessment. Transmission of infection by gastrointestinal endoscopy. Manchester (MA): The Society; 1993.

    12.    Winawer SJ, Taylor N. Healing lessons. New York: Routledge; 1998.