Correspondence
Screening Colonoscopy among Persons 40 to 49 Years of Age
N Engl J Med 2002; 347:1205-1206October 10, 2002
- Article
To the Editor:
Imperiale et al. (June 6 issue)1 presented a well-designed and important study on the effectiveness of screening for colon cancer in persons 40 to 49 years of age. However, the conclusions appear perhaps to be driven more by cost than by effectiveness.
The goal of screening is not only the detection of early colon cancer but also, more important, the identification and removal of precursor adenomas — that is, prevention.2 In their discussion, the authors imply that detecting an adenoma and removing it in a person 40 years of age is equivalent to operating on it, at a curable stage, in a person who is 50, when the lesion would be detected by current screening protocols. This idea does not make sense, whether viewed from the perspective of cost or from the perspective of quality of life, especially if the “curative” surgery ends up being a sphincter-losing abdominoperineal resection.
Tubular adenomas were seen in 8.7 percent of the 906 subjects in this study, a proportion that translates into a number needed to screen of 12. Even if a stricter definition of precursor lesion, such as advanced adenoma, is adopted, we can see that 3.5 percent of the subjects had this lesion (for a number needed to screen of 29) as compared with 4.1 percent of persons 50 to 59 years old (number needed to screen, 24). Data on the natural history of adenomas3 assure us that leaving adenomas in situ for up to 10 years will undoubtedly have consequences in almost 10 percent of patients.
One might question whether the above numbers needed to screen are acceptable from the perspective of society in terms of opportunity costs, but it is inaccurate to conclude that screening in this group is not effective. The political acceptability of early screening should be assessed locally; screening is, in fact, moderately effective in this group.
3 ReferencesJoseph Romagnuolo, M.D.
University of Calgary, Calgary, AB T2N 5S2, Canada
jromagnu@ucalgary.ca 1
Imperiale TF ,Wagner DR ,Lin CY ,Larkin GN ,Rogge JD ,Ransohoff DF . Results of screening colonoscopy among persons 40 to 49 years of age. N Engl J Med 2002;346:1781-1785
Full Text | Web of Science | Medline2
Winawer SJ ,Zauber AG ,Ho MN , et al. Prevention of colorectal cancer by colonoscopic polypectomy. N Engl J Med 1993;329:1977-1981
Full Text | Web of Science | Medline3
Stryker SJ ,Wolff BG ,Culp CE ,Libbe SD ,Ilstrup DM ,MacCarty RL . Natural history of untreated colonic polyps. Gastroenterology 1987;93:1009-1013
Web of Science | Medline
To the Editor:
In the study of screening colonoscopy by Imperiale et al., what were the nature and incidence of the complications, if any, associated with the colonoscopy procedures?
Howard T. Chatterton, M.D., Ph.D.
Marshfield Clinic, Ladysmith, WI 54848
chatterh@mfldclin.edu Author/Editor Response
The authors reply:
To the Editor: Whether 12 or 29 is low or high as a number needed to screen depends in large part on whether the natural history of the lesions identified by screening is ominous. Adenomas found in persons 40 years old are unlikely to lead to many sphincter-losing abdominal perineal resections. Others have used evidence and reasoning similar to ours to suggest that detection of breast cancer in persons under the age of 50 does not necessarily or regularly translate into a benefit when compared with detection of the lesion if screening is begun at the age of 50.1
Whether finding adenomas or early colorectal cancer in persons 40 to 49 years old produces a benefit commensurate with the risk and cost involved depends largely on the prevalence and natural history (i.e., growth rates) of the adenomas found. Studies from the Mayo Clinic2,3 showed that about 10 percent of large lesions (>1 cm) left intact in the colon became cancerous over a period of 10 years, but the histologic features of the initial lesions were not assessed in these studies, which were performed in the era before the widespread use of colonoscopy, and many of the lesions may already have been cancerous when first identified by barium enema. Many were substantially larger than 1 cm.2 Therefore, natural-history data from these studies may not be readily generalized to (and may be more ominous than) what we now term “advanced neoplasms,” including adenomas and lesions smaller than 1 cm. As we discuss in our report, the term “advanced neoplasm” was created not because its natural history is known to be ominous, but rather because clinical researchers (including ourselves4) needed a surrogate end point that occurs more frequently than cancer. Whether the end point currently considered an “advanced neoplasm” is an appropriate surrogate has yet to be determined.
With regard to complications from colonoscopic screening: none were reported in this group. The complication rate in persons over the age of 50 in the Lilly cohort is low, as has been reported previously.4
4 ReferencesThomas F. Imperiale, M.D.
Regenstrief Institute for Health Care, Indianapolis, IN 46202David F. Ransohoff, M.D.
University of North Carolina, Chapel Hill, NC 275991
Fletcher SW. Breast cancer screening among women in their forties: an overview of the issues. In: National Institutes of Health Consensus Conference on breast cancer screening for women ages 40–49. Journal of the National Cancer Institute monographs. No. 22. Bethesda, Md.: National Cancer Institute, 1997:5-9.
2
Stryker SJ ,Wolff BG ,Culp CE ,Libbe SD ,Ilstrup DM ,MacCarty RL . Natural history of untreated colonic polyps. Gastroenterology 1987;93:1009-1013
Web of Science | Medline3
Otchy DP ,Ransohoff DF ,Wolff BG , et al. Metachronous colon cancer in persons who have had a large adenomatous polyp. Am J Gastroenterol 1996;91:448-454
Web of Science | Medline4
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
Full Text | Web of Science | Medline
