Association between Manganese Superoxide Dismutase (MnSOD) Polymorphism and Prostate Cancer Susceptibility: A Meta-Analysis

Background Previous studies have investigated the relationship between manganese superoxide dismutase (MnSOD) Val16Ala polymorphism and prostate cancer susceptibility, but the results have remained controversial. This meta-analysis was therefore performed to clarify this association. Methods The databases PubMed, Embase and Web of Science were searched for relevant available studies. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to evaluate the strength of the association. Publication bias was estimated using Begg's funnel plots and Egger's regression test. Trial sequential analysis was used to reduce the risk of type I error and estimate whether the evidence of the results was sufficient. Results Overall, a significant increased risk of prostate cancer was associated with MnSOD Val16Ala polymorphism for the heterozygote model (OR = 1.14; 95% CI, 1.05-1.24), homozygote model (OR = 1.18; 95% CI, 1.02-1.36), dominant model (OR = 1.24; 95% CI, 1.07-1.44) and recessive model (OR = 1.10; 95% CI, 0.96-1.24). In the subgroup analysis by genotyping method, the results were statistically significant for the TaqMan and PCR-RFLP methods. In addition, when stratified by sample size, statistically significant increased risks were found among both large samples and small samples. Furthermore, when stratified by source of control, significant results were detected in both population-based controls and hospital-based controls. By trial sequential analyses, these findings in the current study were shown to be based on sufficient evidence. Conclusions This meta-analysis indicated that the Ala allele of the MnSOD gene polymorphism increases prostate cancer susceptibility.