Correspondence

Importance of Colonic Adenomas 5 mm or Less in Diameter

N Engl J Med 1997; 336:1761-1762June 12, 1997

Article

To the Editor:

Several studies have suggested that among persons with tubular adenomas detected by sigmoidoscopy that are diminutive (<5 mm in diameter) or small (6 to 9 mm in diameter) there is not a substantial number of advanced adenomas or cancers found proximally at colonoscopy,1,2 nor is there a subsequent increase in the risk of proximal cancer among those who do not undergo colonoscopy.3 Read et al. (Jan. 2 issue)4 found a substantial prevalence of proximal colonic neoplasms, including advanced lesions, in asymptomatic average-risk patients with diminutive rectosigmoid adenomas and concluded that the finding of such adenomas warrants colonoscopy. Unlike previous studies, however, this one did not distinguish between the size of the adenoma and its histologic features. Thus, included among the 137 diminutive distal adenomas were 8 polyps (6 percent) that should have been considered advanced lesions according to the authors' definition (because they had a villous component or moderate-to-severe dysplasia). The prevalence of “advanced” features increased with the size of the index adenoma: 21 percent for small index adenomas (11 of 52) and 36 percent for large distal adenomas (5 of 14). There is agreement that colonoscopy is indicated when patients have adenomas with such features, regardless of their size.5

Because advanced distal adenomas predict advanced proximal lesions, the increasing risk of advanced proximal lesions with the increasing size of distal polyps may largely be explained by the higher prevalence of villous and dysplastic adenomas among larger distal polyps. Likewise, the unexpectedly high prevalence of advanced proximal lesions in the patients with diminutive distal adenomas may have been due to the inclusion of the eight patients with advanced distal adenomas in this group.

It would be helpful if the authors reexamined their data after taking these considerations into account.

Joe V. Selby, M.D., M.P.H.
T.R. Levin, M.D.
Kaiser Permanente Medical Care Program, Oakland, CA 94611

5 References

1. 1

   Grossman S, Milos ML, Tekawa IS, Jewell NP. Colonoscopic screening of persons with suspected risk factors for colon cancer. II. Past history of colorectal neoplasms. Gastroenterology 1989;96:299-306
   Web of Science | Medline

2. 2

   Zarchy TM, Ershoff D. Do characteristics of adenomas on flexible sigmoidoscopy predict advanced lesions on baseline colonoscopy? Gastroenterology 1994;106:1501-1504
   Web of Science | Medline

3. 3

   Atkin WS, Morson BC, Cuzick J. Long-term risk of colorectal cancer after excision of rectosigmoid adenomas. N Engl J Med 1992;326:658-662
   Full Text | Web of Science | Medline

4. 4

   Read TE, Read JD, Butterly LF. Importance of adenomas 5 mm or less in diameter that are detected by sigmoidoscopy. N Engl J Med 1997;336:8-12
   Full Text | Web of Science | Medline

5. 5

   Levin B, Murphy GP. Revisions in American Cancer Society recommendations for the early detection of colorectal cancer. CA Cancer J Clin 1992;42:296-299
   CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: We appreciate the comments of Drs. Selby and Levin, and their concern is valid. Our data, however, do not suggest a correlation between the histologic features of index rectosigmoid adenomas and the prevalence of advanced proximal neoplasia. Of the eight patients with index rectosigmoid adenomas 5 mm or less in diameter who had advanced proximal neoplasms, seven had solitary tubular adenomas in the rectosigmoid, and one had a solitary villous adenoma 2 mm in diameter. Of the five patients with index rectosigmoid adenomas 6 to 10 mm in diameter who had advanced proximal neoplasms, four had solitary tubular adenomas in the rectosigmoid, and one had a solitary tubulovillous adenoma. Therefore, we would not refrain from performing colonoscopy in patients with rectosigmoid adenomas 10 mm or less in diameter because the index rectosigmoid adenoma lacked villous or dysplastic features.

Thomas E. Read, M.D.
Julie D. Read, R.N.
Washington University School of Medicine, St. Louis, MO 63110

Lynn F. Butterly, M.D.
Lahey Hitchcock Medical Center, Burlington, MA 01805