title: Meta-analysis: Circulating vitamin D and ovarian cancer risk.
abstract: OBJECTIVE
  To review and summarize evidence from longitudinal studies on the association between circulating 25 hydroxyvitamin D (25(OH)D) and the risk of ovarian cancer (OC).
  
  
  METHODS
  Relevant prospective cohort studies and nested case-control studies were identified by systematically searching Ovid Medline, EMBASE, and ISI Web of Knowledge databases and by cross-referencing. The following data were extracted in a standardized manner from eligible studies: first author, publication year, country, study design, characteristics of the study population, duration of follow-up, OC incidence according to circulating vitamin D status and the respective relative risks, and covariates adjusted for in the analysis. Due to the heterogeneity of studies in categorizing circulating vitamin D levels, all results were recalculated for an increase of circulating 25(OH)D by 20ng/ml. Summary relative risks (RRs) were calculated using meta-analysis methods.
  
  
  RESULTS
  Overall, ten individual-level studies were included that reported on the association between circulating vitamin D levels and OC incidence. Meta-analysis of studies on OC incidence resulted in a summary RR (95% confidence interval, CI) of 0.83 (0.63-1.08) for an increase of 25(OH)D by 20ng/ml (P=0.160). No indication for heterogeneity and publication bias was found.
  
  
  CONCLUSIONS
  A tentative inverse association of circulating 25(OH)D with OC incidence was found, which did not reach statistical significance but which requires clarification by additional studies due to potentially high clinical and public health impact.
authors.affiliation: Division of Clinical Epidemiology and Aging Research, German Cancer Research Center, Bergheimer Strasse 20, D-69115 Heidelberg, Germany.
authors.forename: Lu
authors.initials: L
authors.lastname: Yin
authors.forename: Norma
authors.initials: N
authors.lastname: Grandi
authors.forename: Elke
authors.initials: E
authors.lastname: Raum
authors.forename: Ulrike
authors.initials: U
authors.lastname: Haug
authors.forename: Volker
authors.initials: V
authors.lastname: Arndt
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
mesh_terms: D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D010051:Ovarian Neoplasms / Q000097:blood*; D012307:Risk Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D