New England Journal Of Medicine Reports Calcium Supplements Help Prevent Polyp Recurrence; DMS Led Study

January 14, 1999

HANOVER, NH -- Men and women who take calcium supplements may have a lower risk of large bowel adenomas, polyps that are considered cancer precursors, reports a study led by Dartmouth Medical School and published today (Jan. 14) in The New England Journal of Medicine.

The results of the clinical study demonstrate that supplementation with calcium can reduce the recurrence rate of large bowel adenomas in people with a history of these particular polyps. The findings suggest promising measures that are fairly simple and inexpensive to help prevent a relatively common cancer.

Dr. John A. Baron, professor of medicine and of community and family medicine at Dartmouth Medical School, led this multi-centered study, funded by the National Institutes of Health. Dartmouth Medical School was the coordinating center for this clinical trial, designed to assess the benefits of calcium supplementation in patients with previously documented polyps.

"Adenomas or polyps may develop into colorectal cancer. Less than one year into the study, we saw positive results from calcium -- fewer adenomas and so, less potential for cancer," said Baron.

Although most polyps in the large bowel are benign, they are thought to be precursors of most colorectal cancers and can be removed before progression to invasive cancer. Colon and rectal cancers (together often referred to as colorectal cancer) are the second-leading cause of cancer death in the U.S., according to Baron.

The study followed 832 patients over a four-year period. Patients were randomized to take either calcium carbonate supplements (1200 milligrams of elemental calcium) or an identical-looking placebo.

As early as the first follow-up, about nine months after the beginning of the trial, the benefits of calcium were noted. Overall, there was a 19% decrease in the incidence of recurrence of one polyp and a 24% decrease in the number of polyps.

During 1998, new cases of colon and rectal cancers were detected in an estimated 67,000 women and 64,600 men, according to the American Cancer Society, and the cancers were responsible for approximately 28,600 deaths in women and 27,900 deaths in men. Altogether colorectal cancer accounted for about 11% of new cases of cancer reported in 1998 and about 10% of all deaths from cancer. The overall incidence of colorectal cancers, however, has declined in the past decade, possibly a result of better screening and increased polyp removal. Age, gender, or baseline intake of calcium, fat or fiber did not alter the effect of calcium supplementation in the study. The trial was double blind: neither patients nor those following them knew which treatment they were taking.

The average age of the participating patients was 61 years; 72% were men. Patients underwent two colonoscopies to view inside the large bowel and assess the effects of calcium. The reduced risk with calcium supplementation, already apparent at the first colonoscopy, continued throughout the four-year trial period. Medical complaints and complications were not associated with the use of calcium supplements.

The study provides the most compelling evidence to date of the potential benefits of calcium in reducing adenomas, which are likely precursors of most colorectal cancers. Earlier studies in humans and animals indicated positive effects, but this investigation provides direct experimental results in human subjects.

Baron notes, "Epidemiological data regarding the association between dietary calcium and the risk of colorectal cancer have varied considerably, but in aggregate are consistent with the effect we observed." Nonetheless, he stresses that the findings do not change the requirement for those at risk to be screened as recommended by their physicians.

Other Dartmouth authors of the paper include Dr. Richard Rothstein, professor and chief of gastroenterology, who headed of the Dartmouth portion of the study; Dr. E. Robert Greenberg, professor of community and family medicine, who heads the Norris Cotton Cancer Center; and Dr. Michael Beach, assistant professor of anesthesiology and of community and family medicine, who is also at the White River Junction Veterans Affairs Medical Center.

In addition to Dartmouth-Hitchcock Medical Center, the other participating centers were: the Cleveland Clinic Foundation, the University of Southern California/Southern California Permanente Medical Group, the University of Iowa, the University of Minnesota, and the University of North Carolina.

The Geisel School of Medicine at Dartmouth

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