The multi-center study, reported in the June 16 issue of the Journal of the National Cancer Institute, builds on prior Dartmouth research and provides more evidence that calcium supplementation appears to be a relatively safe and inexpensive way to reduce the risk of the most serious types of colorectal polyps.
"Our results suggest that calcium supplementation may have a more protective effect on advanced adenomas than on other types of colorectal polyps," said Kristin Wallace, a Dartmouth Medical School (DMS) graduate student who was the lead author on the study. "These findings highlight the need to consider 'polyp type' when assessing the efficacy of a given treatment."
John Baron, MD, professor of medicine and of community and family medicine at DMS and an investigator at Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center, has done numerous studies on the effects of aspirin and calcium on colon cancer and led the project . "Previous studies have demonstrated an association between calcium intake and moderate decreases in the risk of precancerous colorectal tumors, but this is the first randomized trial to evaluate the effect of calcium on different types of colorectal lesions," he said.
Colorectal polyps, or adenomas, are bumps or fleshy tumors that occur on the inside lining of the colon that may become cancerous over time. By decreasing the size of the polyps and their number, there is less potential for colorectal cancer.
Researchers analyzed data from 913 patients enrolled in the Calcium Polyp Prevention Study, a randomized, double-blind, placebo-controlled trial - meaning that neither the patient nor the those following them knew which treatment they were receiving. Patients took either a 1200 mg calcium supplement or a placebo and had a follow-up colonoscopy one and four years after enrolling in the trial.
The results showed that supplemental calcium slightly decreased the risk of all types of colorectal polyps, but effect was greatest for the most advanced colorectal lesions. There was also some evidence that a diet high in fiber and low in fat increased the preventive effect of calcium, but these results were not statistically definitive.
The research was supported by the National Cancer Institute, the National Institutes of Health and the Department of Health and Human Services. Other Dartmouth Medical School researchers who contributed to this study include Bernard Cole, PhD, Margaret Karagas, PhD, Michael Beach, MD, PhD, Loretta Pearson, M. Phil. and Richard Rothstein, MD.
In addition to Dartmouth-Hitchcock Medical Center, the other participating centers were the Cleveland Clinic Foundation, the University of Southern California School of Medicine, the University of Minnesota, the University of North Carolina School of Medicine and Emory University.
Journal
JNCI Journal of the National Cancer Institute