title: Prolonged effect of calcium supplementation on risk of colorectal adenomas in a randomized trial.
abstract: BACKGROUND
  Calcium supplementation has been shown to decrease the risk of recurrence of colorectal adenomas in randomized trials. However, the duration of this protective effect after cessation of active supplementation is not known.
  
  
  METHODS
  In the Calcium Polyp Prevention Study, 930 subjects with a previous colorectal adenoma were randomly assigned from November 1988 through April 1992 to receive placebo or 1200 mg of elemental calcium daily for 4 years. The Calcium Follow-up Study was an observational phase of the trial that tracked adenoma occurrence for an average of 7 years after the end of randomized treatment and gathered information regarding the use of medications, vitamins, and supplements during that time. We obtained follow-up information for 822 subjects, 597 of whom underwent at least one colonoscopy after the end of study treatment and are included in this analysis. Generalized linear models were used to compute relative risks (RRs) and 95% confidence intervals (CIs) for the effect of randomized calcium treatment on risk of adenoma recurrence during the first 5 years after study treatment ended and during the subsequent 5 years. Statistical tests were two-sided.
  
  
  RESULTS
  During the first 5 years after randomized treatment ended, subjects in the calcium group still had a substantially and statistically significantly lower risk of any adenoma than those in the placebo group (31.5% versus 43.2%; adjusted RR = 0.63, 95% CI = 0.46 to 0.87, P = .005) and a smaller and not statistically significant reduction in risk of advanced adenomas (adjusted RR = 0.85, 95% CI = 0.43 to 1.69, P = .65). However, the randomized treatment was not associated with the risk of any type of polyp during the next 5 years. The findings were broadly similar when the analysis was restricted to subjects who did not report use of any calcium supplements after the treatment phase of the trial ended.
  
  
  CONCLUSIONS
  The protective effect of calcium supplementation on risk of colorectal adenoma recurrence extends up to 5 years after cessation of active treatment, even in the absence of continued supplementation.
authors.affiliation: Department of Community and Family Medicine, Dartmouth Medical School, Lebanon, NH, USA.
authors.forename: Maria V
authors.initials: MV
authors.lastname: Grau
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sandler
authors.forename: Kristin
authors.initials: K
authors.lastname: Wallace
authors.forename: Robert W
authors.initials: RW
authors.lastname: Haile
authors.forename: Timothy R
authors.initials: TR
authors.lastname: Church
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Beck
authors.forename: Robert W
authors.initials: RW
authors.lastname: Summers
authors.forename: Elizabeth L
authors.initials: EL
authors.lastname: Barry
authors.forename: Bernard F
authors.initials: BF
authors.lastname: Cole
authors.forename: Dale C
authors.initials: DC
authors.lastname: Snover
authors.forename: Richard
authors.initials: R
authors.lastname: Rothstein
authors.forename: Jack S
authors.initials: JS
authors.lastname: Mandel
mesh_terms: D000236:Adenoma / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D000368:Aged; D016588:Anticarcinogenic Agents / Q000008:administration & dosage*; D002136:Calcium, Dietary / Q000008:administration & dosage*; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*; D019587:Dietary Supplements; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control; D016017:Odds Ratio; D012107:Research Design; D018570:Risk Assessment; D013997:Time Factors
chemical_list: D016588:Anticarcinogenic Agents; D002136:Calcium, Dietary