The aim of this meta-analysis was to explore the association between the
manganese superoxide dismutase (MnSOD) gene polymorphism and
breast cancer risk, and to investigate the interaction of this gene polymorphism with known risk factors for
breast cancer. Crude odds ratios (
ORs) with 95% confidence intervals (CIs) for
breast cancer risk associated with co-dominant models [
valine/
alanine (Val/Ala) vs.
Val/Val,
Ala/Ala vs.
Val/Val], a dominant model (Val/
Ala + Ala/Ala vs.
Val/Val) and a recessive model (
Ala/Ala vs. Val/Ala +
Val/Val) were statistically estimated. This meta‑analysis included 8,102
breast cancer cases and 9,740 controls from 14 published case-control studies. The data revealed no significant association between the MnSOD polymorphism and the risk of developing
breast cancer. However, upon subgroup analyses, the risk was significantly increased in premenopausal women with the dominant model of the MnSOD gene polymorphism (OR, 1.15; 95% CI, 1.01-1.31). Statistically significant increased risks were also identified in women with the MnSOD genotypes containing the Ala allele who had a tobacco smoking history (OR, 1.17; 95% CI, 1.02-1.34), a higher body mass index (OR, 1.26; 95% CI, 1.02-1.56) or who used
oral contraceptives (OR, 1.98; 95% CI, 1.34-2.93). By contrast, there was no significant association between
breast cancer risk and alcohol consumption and ethnicity. This meta‑analysis demonstrated no statistically significant association between the MnSOD gene polymorphism and
breast cancer susceptibility, except in premenopausal women with certain unhealthy lifestyle habbits.