Meta-analysis: Circulating vitamin D and ovarian cancer risk

ObjectiveTo 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).MethodsRelevant 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 20 ng/ml. Summary relative risks (RRs) were calculated using meta-analysis methods.ResultsOverall, 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 20 ng/ml (P = 0.160). No indication for heterogeneity and publication bias was found.ConclusionsA 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.

Research Highlights
► As we know, this is the first systematic review and meta-analysis evaluating the association between serum 25(OH)D levels and ovarian cancer risk.
► The method for comprehensive trend estimation from summarized dose–response data was used for combining all results from individual studies so far.
► A potential weak inverse association between serum vitamin D and ovarian cancer risk was found in this meta-analysis.