Effect of calcium supplementation on the risk of large bowel polyps.
BACKGROUND
Clinical trials have shown that calcium supplementation modestly decreases the risk of colorectal adenomas. However, few studies have examined the effect of calcium on the risk of different types of colorectal lesions or dietary determinants of this effect.


METHODS
Our analysis used patients from the Calcium Polyp Prevention Study, a randomized, double-blind, placebo-controlled chemoprevention trial among patients with a recent colorectal adenoma. Nine hundred thirty patients were randomly assigned to calcium carbonate (1200 mg/day) or placebo. Follow-up colonoscopies were conducted approximately 1 and 4 years after the qualifying examination. We used general estimating equation (GEE) and generalized linear regression analyses to compute risk ratios and 95% confidence intervals (CIs) to assess the effect of calcium treatment versus placebo on the risk of hyperplastic polyps, tubular adenomas, and more advanced lesions. Additionally, we used GEE analyses to compare the calcium treatment effects for various types of polyps with that for tubular adenomas. We also examined the interaction between calcium treatment and baseline intake of dietary calcium, fat, and fiber. All P values were obtained using Wald tests based on the corresponding models. All tests of statistical significance were two-sided.


RESULTS
The calcium risk ratio for hyperplastic polyps was 0.82 (95% CI = 0.67 to 1.00), that for tubular adenomas was 0.89 (95% CI = 0.77 to 1.03), and that for histologically advanced neoplasms was 0.65 (95% CI = 0.46 to 0.93) compared with patients assigned to placebo. There were no statistically significant differences between the risk ratio for tubular adenomas and that for other types of polyps. The effect of calcium supplementation on adenoma risk was most pronounced among individuals with high dietary intakes of calcium and fiber and with low intake of fat, but the interactions were not statistically significant.


CONCLUSIONS
Our results suggest that calcium supplementation may have a more pronounced antineoplastic effect on advanced colorectal lesions than on other types of polyps.
Wallace
Kristin
K
Department of Community and Family Medicine, Dartmouth-Hitchcock Medical Center, Lebanon, NH, USA.
Baron
John A
JA
Cole
Bernard F
BF
Sandler
Robert S
RS
Karagas
Margaret R
MR
Beach
Michael A
MA
Haile
Robert W
RW
Burke
Carol A
CA
Pearson
Loretta H
LH
Mandel
Jack S
JS
Rothstein
Richard
R
Snover
Dale C
DC
D011125:Adenomatous Polyposis Coli / Q000473:pathology / Q000517:prevention & control*; D000328:Adult; D000368:Aged; D017610:Calcium Compounds / Q000008:administration & dosage* / Q000494:pharmacology*; D003111:Colonic Polyps / Q000188:drug therapy* / Q000473:pathology; D003113:Colonoscopy; D019587:Dietary Supplements; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000517:prevention & control*; D016017:Odds Ratio; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment
D017610:Calcium Compounds