title: Meta-analysis: folic acid in the chemoprevention of colorectal adenomas and colorectal cancer.
abstract: BACKGROUND
  Folic acid has been identified as a possible agent for the chemoprevention of colorectal cancer.
  
  
  OBJECTIVE
  To assess the effectiveness of folic acid in reducing the recurrence of adenomas (precursors of colorectal cancer) among populations with a history of adenomas and the incidence of colorectal cancer within average-risk populations.
  
  
  METHODS
  Systematic review of randomized controlled trials comparing folic acid alone, or with other agents, vs. placebo. Eight databases were searched for relevant trials. Meta-analysis was performed.
  
  
  RESULTS
  The literature search retrieved 3785 citations. Six studies met the inclusion criteria. Meta-analysis of three studies in individuals with a history of adenomas showed no statistically significant difference in the relative risk of adenoma recurrence (RR 0.93, P = 0.27). A sensitivity analysis of the two higher quality trials changed the direction of effect (RR 1.16, P = 0.11). Meta-analysis of three trials in general populations demonstrated no statistically significant effect on the relative risk of colorectal cancer (RR 1.13, P = 0.54). In all three analyses, outcome event rates were higher in individuals receiving folic acid.
  
  
  CONCLUSIONS
  There is no evidence that folic acid is effective in the chemoprevention of colorectal adenomas or colorectal cancer for any population.
authors.affiliation: Health Economics and Decision Science, School of Health and Related Research, University of Sheffield, Sheffield, UK. c.carroll@shef.ac.uk
authors.forename: C
authors.initials: C
authors.lastname: Carroll
authors.forename: K
authors.initials: K
authors.lastname: Cooper
authors.forename: D
authors.initials: D
authors.lastname: Papaioannou
authors.forename: D
authors.initials: D
authors.lastname: Hind
authors.forename: P
authors.initials: P
authors.lastname: Tappenden
authors.forename: H
authors.initials: H
authors.lastname: Pilgrim
authors.forename: A
authors.initials: A
authors.lastname: Booth
mesh_terms: D000236:Adenoma / Q000517:prevention & control*; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D015179:Colorectal Neoplasms / Q000517:prevention & control*; D005492:Folic Acid / Q000008:administration & dosage / Q000627:therapeutic use*; D006801:Humans; D016032:Randomized Controlled Trials as Topic
chemical_list: D005492:Folic Acid