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Colonoscopic Screening of Women for Colorectal Neoplasia
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     To the Editor: In the report by Schoenfeld et al. (May 19 issue)1 on the Colorectal Neoplasia Screening with Colonoscopy in Average-Risk Women at Regional Naval Medical Centers (CONCeRN) study, the investigators conclude that colonoscopy is the best test for women, because flexible sigmoidoscopy is less sensitive for advanced proximal colorectal neoplasia, relative to the sensitivity of flexible sigmoidoscopy for detecting this neoplasia in men. Patients, however, are concerned about absolute risk, not relative risk. Overall, the absolute risk of having an advanced neoplasm was lower in women than in men, and fewer women had advanced proximal neoplasia.1,2 Furthermore, the natural history of the advanced colonic neoplasm is unknown. Cancer and high-grade dysplasia are more clearly ominous, but their relationships to age and location are not reported for the CONCeRN study. In the initial study, the Veterans Affairs Cooperative Study 380, 81 of 3121 men had cancer or high-grade dysplasia, including 30 cancers2; in the CONCeRN study, 10 of 1463 women had cancer or high-grade dysplasia, including only 1 cancer.

    We3 and others4 have shown that age is a better predictor of advanced proximal neoplasia than sex. A policy of tailoring proximal colonic screening to men and women older than 65 years of age would be a more effective use of health care resources than performing colonoscopy in all women, without regard to age.5

    Theodore R. Levin, M.D.

    Permanente Medical Group

    Oakland, CA 94612

    Wendy S. Atkin, Ph.D.

    St Mark's Hospital

    Harrow HA1 3UJ, United Kingdom

    References

    Schoenfeld P, Cash B, Flood A, et al. Colonoscopic screening of average-risk women for colorectal neoplasia. N Engl J Med 2005;352:2061-2068.

    Lieberman DA, Weiss DG, Bond JH, Ahnen DJ, Garewal H, Chejfec G. Use of colonoscopy to screen asymptomatic adults for colorectal cancer. N Engl J Med 2000;343:162-168.

    Levin TR, Palitz A, Grossman S, et al. Predicting advanced proximal colonic neoplasia with screening sigmoidoscopy. JAMA 1999;281:1611-1617.

    Imperiale TF, Wagner DR, Lin CY, Larkin GN, Rogge JD, Ransohoff DF. Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings. N Engl J Med 2000;343:169-174.

    UK Flexible Sigmoidoscopy Screening Trial Investigators. Single flexible sigmoidoscopy screening to prevent colorectal cancer: baseline findings of a UK multicentre randomised trial. Lancet 2002;359:1291-1300.

    To the Editor: Schoenfeld et al. point out important differences between women and men regarding the distribution of adenomas in the colon, once again reinforcing the finding that the sensitivity of colonoscopy is superior to that of flexible sigmoidoscopy. Limiting the definition of the distal colon to the sigmoid and rectum probably underestimates the area examined by skilled providers, and the completion of 98.7 percent of colonoscopies probably overestimates the completion rate in usual care facilities in the community. At this point in the debate about colon-cancer screening, the more pertinent questions relate to the marginal cost and morbidity associated with colonoscopic screening, so that the risks can be balanced against the benefits. In addition, we will need a plan to train a large number of qualified endoscopists to meet the demands of a colonoscopy program. Concurrently, we need to develop approaches to improve patients' adherence to screening recommendations. Even if we define the ideal screening strategy, its performance will be dismal if fewer than half the eligible population participates in screening.1

    Colin M. Thomas, M.D., M.P.H.

    University of California, San Diego, School of Medicine

    San Diego, CA 92161

    References

    Colorectal cancer test use among persons aged > or = 50 years -- United States, 2001. MMWR Morb Mortal Wkly Rep 2003;52:193-196.

    The authors reply: Drs. Levin and Atkin state that patients are concerned about absolute risk of missed cases of advanced colonic neoplasia. However, the absolute risk of missing advanced neoplasia is greater in women than men if both groups undergo flexible sigmoidoscopy. Our data show that more men who were 50 to 59 years of age had advanced neoplasia than women of the same age (4.7 percent vs. 2.9 percent, respectively; P=0.15). However, since flexible sigmoidoscopy identifies far more cases of advanced neoplasia in men than women (71.4 percent vs. 30.0 percent, P=0.002), the absolute risk of missing advanced neoplasia is higher among women who are 50 to 59 years of age than among men in the same age range. For example, if 1000 50-to-59-year-old men underwent flexible sigmoidoscopy, advanced neoplasia would be detected in 34 men and missed in 13. However, if 1000 50-to-59-year-old women underwent flexible sigmoidoscopy, then advanced neoplasia would be detected in 9 women and missed in 20. These data do not support "tailoring" colorectal-cancer screening to flexible sigmoidoscopy for women younger than 65 years of age.1 On the basis of our data, we think that colonoscopy is the best tool to identify advanced colonic neoplasia in both men and women, and we believe that colonoscopy should be the preferred colorectal-cancer screening tool.

    The natural history of the advanced colonic neoplasm is poorly understood. We do not know what proportion of cases of advanced colonic neoplasia develop into invasive colon cancer. Nevertheless, we think that it is preferable to identify and remove the precancerous lesion or advanced colonic neoplasia in order to prevent colorectal cancer, and colonoscopy is the most accurate tool to accomplish this goal.

    We agree with Dr. Thomas that ideal screening strategies require strong adherence, and ongoing research will address this issue. However, we disagree with his comment about the depth of insertion of the flexible sigmoidoscope. The best available data2 indicate that scopes do not pass beyond the sigmoid–descending colon junction in the majority of patients undergoing flexible sigmoidoscopy.

    Philip Schoenfeld, M.D.

    University of Michigan School of Medicine

    Ann Arbor, MI 48105

    pschoenf@umich.edu

    David Lieberman, M.D.

    Oregon Health Sciences University

    Portland, OR 97201

    References

    Imperiale TF, Wagner DR, Lin CY, Larkin GN, Rogge JD, Ransohoff DF. Risk of advanced proximal neoplasms in asymptomatic adults according to the distal colorectal findings. N Engl J Med 2000;343:169-174.

    Painter J, Saunders DB, Bell GD, Williams CB, Pitt R, Bladen J. Depth of insertion at flexible sigmoidoscopy: implications for colorectal cancer screening and instrument design. Endoscopy 1999;31:227-231.