CORRESPONDENCE

Diet and Cancer Prevention

Richard Nelson, Victoria Persky, Mary Turyk

Affiliations of authors: R. Nelson (Department of Surgery and School of Public Health), V. Persky, M. Turyk (School of Public Health), University of Illinois at Chicago.

Correspondence to: Richard Nelson, M.D., F.A.C.S., Department of Surgery and School of Public Health, University of Illinois at Chicago, Rm. 2204 M/C 957, 1740 West Taylor, Chicago, IL (e-mail: altohorn{at}uic.edu).

Recent articles and commentaries in the Journal cast doubt on the dietary prevention of cancer (14). Is this pessimism really justified?

Migration studies of populations moving from low-incidence to high-incidence locales (such as Japanese to Hawaii) suggested that dietary factors existed that altered colorectal cancer risk. The rapid increase in the incidence of colorectal cancer incidence throughout the first 13 years of the Surveillance, Epidemiology, and End Results (SEER) Program1 (1973 through 1986; a National Center for Health Statistics program for monitoring cancer incidence and outcomes in the United States beginning in 1973) added urgency to define these dietary factors. However, SEER reported that the rapidly rising incidence of colorectal cancer in the United States suddenly reversed in 1986, and since then the incidence has declined at a rate greater than 1% per year. More than a 25% drop in the incidence of distal colorectal cancer occurred in white men and women from 1986 through 1994 (Fig. 1Go). Prevention of colorectal cancer is clearly occurring here in the United States (5).



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Fig. 1. Distal colorectal cancer incidence from 1973 through 1994 by race and sex (Surveillance, Epidemiology, and End Results Program). Distal cancer is defined as adenocarcinoma located from the sigmoid colon to the distal rectum, excluding the anal canal.

 
This reversal in trend provided a unique opportunity to determine what happened in the United States to cause this change in a time trend study of all suspected risk factors for colorectal cancer. The focus was on data representative of the whole U.S. population, beginning 15 years before the change in cancer trend, in 1971, both because there is a considerable lag time from exposure to tumor formation and diagnosis and because it was at that time that most nationally representative data became available through the National Health and Nutrition Examination Surveys. Unlike the studies cited in the "News" section of the Journal (2), the dietary factor most supportive of the decline in colorectal cancer incidence in this time trend study was fiber. Other factors clearly played a role, the most important being the increasing use of colonoscopic polypectomy (5).

In judging therapeutic efficacy, the randomized, controlled clinical trial is thought to be the method least subject to bias in evidence gathering. By analogy, this design has been used in cancer prevention studies, but perhaps with less efficacy, which may be due to recruitment of atypical subject populations or substitution of surrogate endpoints for cancer, as in the polyp prevention trials cited (2,3). However, in spite of the inability of the trials and analytic studies described in the Journal (14) to provide a generally accepted template for colorectal cancer prevention, prevention, as stated above, is occurring.

NOTES

1 Editor's note: SEER is a set of geographically defined, population-based, central cancer registries in the United States, operated by local nonprofit organizations under contract to the National Cancer Institute (NCI). Registry data are submitted electronically without personal identifiers to the NCI on a biannual basis, and the NCI makes the data available to the public for scientific research. Back

REFERENCES

1 Feskanich D, Ziegler RG, Michaud DS, Giovannucci EL, Speizer FE, Willett WC, et al. Prospective study of fruit and vegetable consumption and risk of lung cancer among men and women. J Natl Cancer Inst 2000;92:1812–23.[Abstract/Free Full Text]

2 Clark G. Recent studies cloud link between diet and cancer [news]. J Natl Cancer Inst 2000;92:1794–5.[Free Full Text]

3 Flood A, Schatzkin A. Colorectal cancer: does it matter if you eat your fruits and vegetables? [editorial]. J Natl Cancer Inst 2000;92:1706–7.[Free Full Text]

4 Michels KB, Giovannucci E, Joshipura KJ, Rosner BA, Stampfer MJ, Fuchs CS, et al. Prospective study of fruit and vegetable consumption and incidence of colon and rectal cancers. J Natl Cancer Inst 2000;92:1740–52.[Abstract/Free Full Text]

5 Nelson RL, Persky V, Turyk M. Determination of factors responsible for the declining incidence of colorectal cancer. Dis Colon Rectum 1999;42:741–52.[Medline]



             
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