Association Between ESR1 XBAI and Breast Cancer Susceptibility: A Systematic Review and Meta-Analysis.

PURPOSE Estrogen receptor 1 (ESR1) XbaI polymorphisms may affect breast cancer susceptibility; however, the results of previously published studies are inconsistent. This meta-analysis aimed to investigate the relationship between ESR1 XbaI polymorphism and breast cancer risk.  Methods: Articles from the PubMed, Embase, Cochrane Library, WoS, Scopus, Wanfang Data, CNKI, CBM and CQVIP databases were systematically searched to determine the association between ESR1 XbaI polymorphism and breast cancer risk. The pooled results were assessed using odds ratios (ORs) and 95% confidence intervals (CIs), followed by subgroup analysis.  Results: Twenty-two studies involving 12,821 cases and 14,739 control subjects were analyzed. The pooled results indicated that ESR1 XbaI polymorphism may decrease risk of breast cancer in AG vs. AA (co-dominant model: OR = 0.88, 95% CI = 0.79-0.97, P = 0.015) and AG + GG vs. AA models (dominant model: OR = 0.89, 95% CI = 0.80-0.98, P = 0.022). Subgroup analysis indicated significant associations between the ESR1 XbaI polymorphism and breast cancer risk were observed in Asian subjects, non-Hardy-Weinberg equilibrium study, post-menopausal status and hospital-based subgroups under the AG vs. AA and AG + GG vs. AA models (all P < 0.05).  Conclusions: Our analysis of pooled data indicated that AG genotype in ESR1 XbaI may be a protective factor for breast cancer patients in some subgroups.