EMBARGOED FOR RELEASE
Wednesday, April 19, 2000
5:00 p.m. EST
NCI Press Office
Arizona Cancer Center
Trials Show No Effect of Low-Fat, High-Fiber, and High-Fruit and -Vegetable Diets
on the Growth of New Colorectal Polyps in People With a History of Precancerous Polyps
- Development of colorectal cancer takes decades, and an intervention of three to four years may not be long enough to make a difference. Continuing follow-up of these patients may lead to further understanding of the long-term impact of dietary interventions.
- Participants in these studies all had at least one polyp previously removed. Nutritional factors may influence critical molecular, cellular, or tissue-level events in colorectal cancer formation well before polyps are formed.
- In these studies, the recurrent polyps - the new polyps that develop after the first ones are removed - tended to be small. Dietary changes might affect only the growth of small polyps into large polyps or large polyps into invasive cancer.
The investigators emphasized that a diet high in fiber, fruits, and vegetables and low in fat can improve overall health and reduce the risk of chronic diseases, including heart disease, hypertension, diabetes, and others. The studies published today looked at a specific scientific question - namely, does dietary change affect recurrence of colorectal polyps - in a group of people who already had polyps.
The Polyp Prevention Trial was funded by NCI and took place at eight clinical centers across the United States: State University of New York at Buffalo, Buffalo, N.Y.; Edward Hines Jr. Hospital, Veterans Administration Medical Center, Hines, Ill.; Kaiser Foundation Research Institute, Oakland, Calif.; Memorial Sloan-Kettering Cancer Center, New York; University of Pittsburgh, Pittsburgh, Pa.; University of Utah, Salt Lake City; Wake Forest University Baptist Medical Center, Winston-Salem, N.C.; and Walter Reed Army Medical Center, Washington, D.C.
About two-thirds of the participants in the Polyp Prevention Trial were male and about
10 percent were minorities. The average age when they joined the trial was 62.
The Wheat Bran Fiber Study was funded by NCI, headed by the Arizona Cancer Center, and carried out by the Phoenix Colon Cancer Prevention Physician Network. About two-thirds of the participants were male, and about 3 percent were minorities. The average age when they joined the study was 66.
The investigators are grateful to the study participants for their contribution to these studies, which required participants to be consistent in the changes in their diets over a long period of time.
NCI is sponsoring a number of prevention trials in which drugs or nutritional supplements are being tested to reduce risk of developing polyps and/or colorectal cancer. Agents under study include sulindac and celecoxib (anti-inflammatory agents that inhibit an enzyme known as cyclo-oxygenase), and the nutrients folic acid and calcium.
Lanza noted, "Until we have the results of these new trials, the only proven way to prevent colorectal cancer is routine screenings for the detection and removal of polyps."
To learn more about participating in prevention trials or about colorectal cancer, contact NCI's Cancer Information Service at 1-800-4-CANCER or visit NCI's Web site at http://www.cancer.gov.
Attachment: Questions and Answers: The Polyp Prevention Trial and the Wheat Bran Fiber Study
Schatzkin A, Lanza E, Corle D, et al. Lack of effect of a low-fat, high-fiber diet on the recurrence of colorectal adenomas. N Engl J Med 2000:342:1149-55.
Alberts DS, Martinez ME, Roe DJ, et al. Lack of effect of a high-fiber cereal supplement on the recurrence of colorectal adenomas. N Engl J Med 2000:342:1156-62.