Association between vitamin D receptor poly(A) polymorphism and breast cancer risk: a meta-analysis

Vitamin D receptor (VDR) poly(A) is a common genetic polymorphism in the VDR gene, and it has been implicated to be associated with breast cancer risk. However, previous studies on the association reported inconclusive results. We performed this meta-analysis to comprehensively assess the association. Eligible studies were searched in PubMed and EMBASE databases. Odds ratio (OR) and its 95 % confidence interval (95 % CI) were used for statistical analysis. A total 6,631 cases and 6,718 controls from 11 case-control studies were finally included into the meta-analysis. Meta-analysis of total eligible studies showed that VDR poly(A) polymorphism was not associated with the risk of breast cancer (S versus L: OR = 0.99, 95 % CI of 0.90-1.09, P = 0.84; SS versus LL: OR = 0.96, 95 % CI of 0.79-1.18, P = 0.70; SS/LS versus LL: OR = 0.96, 95 % CI of 0.83-1.12, P = 0.63; SS versus LL/LS: OR = 1.00, 95 % CI of 0.91-1.10, P = 0.98). Meta-analysis of studies with high quality also showed that there was no association between VDR poly(A) polymorphism and breast cancer risk. In addition, in the subgroup analysis by ethnicity, no significant association was found among Caucasians. Therefore, the meta-analysis suggests that VDR poly(A) polymorphism is not associated with the risk of breast cancer. Large well-designed studies are necessary to clarify the possible association in Asians.