The rs9340799 polymorphism of the estrogen receptor alpha (ESR1) gene and its association with breast cancer susceptibility.

The ESR1 rs9340799 polymorphism has been frequently investigated with regard to its association with breast cancer (BC) susceptibility, but the findings have been inconclusive. In this work, we aimed to address the inconsistencies in study findings by performing a systematic review and meta-analysis. Eligible studies were identified from the Web of Science, PubMed, Scopus, China National Knowledge Infrastructure, VIP and Wanfang databases based on the predefined inclusion and exclusion criteria. The pooled odds ratio (OR) was then calculated under five genetic models: homozygous (GG vs. AA), heterozygous (AG vs. AA), dominant (AG + GG vs. AA), recessive (GG vs. AA + AG) and allele (G vs. A). Combined results from 23 studies involving 34,721 subjects indicated a lack of significant association between the polymorphism and BC susceptibility (homozygous model, OR = 1.045, 95% CI 0.887–1.231, P = 0.601; heterozygous model, OR = 0.941, 95% CI 0.861–1.030, P = 0.186; dominant model, OR = 0.957, 95% CI 0.875–1.045, P = 0.327; recessive model, OR = 1.053, 95% CI 0.908–1.222, P = 0.495; allele model, OR = 0.987, 95% CI 0.919–1.059, P = 0.709). Subgroup analyses by ethnicity, menopausal status and study quality also revealed no statistically significant association (P > 0.05). In conclusion, our results showed that the ESR1 rs9340799 polymorphism was not associated with BC susceptibility, suggesting its limited potential as a genetic marker for BC.