Glutathione S-transferase M1 polymorphism and esophageal cancer risk: An updated meta-analysis based on 37 studies.

AIM: To evaluate the relationship between glutathione S-transferase M1 (GSTM1) polymorphism and susceptibility to esophageal cancer (EC). METHODS: A comprehensive search of the United States National Library of Medicine PubMed database and the Elsevier, Springer, and China National Knowledge Infrastructure databases for all relevant studies was conducted using combinations of the following terms: "glutathione S-transferase M1", "GSTM1", "polymorphism", and "EC" (until November 1, 2014). The statistical analysis was performed using the SAS software (v.9.1.3; SAS Institute, Cary, NC, United States) and the Review Manager software (v.5.0; Oxford, England); crude odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the association between the GSTM1 null genotype and the risk of EC. RESULTS: A total of 37 studies involving 2236 EC cases and 3243 controls were included in this meta-analysis. We observed that the GSTM1 null genotype was a significant risk factor for EC in most populations (OR = 1.33, 95%CI: 1.12-1.57, P heterogeneity < 0.000001, and I (2) = 77.0%), particularly in the Asian population (OR = 1.53, 95%CI: 1.26-1.86, P heterogeneity < 0.000001, and I (2) = 77.0%), but not in the Caucasian population (OR = 1.02, 95%CI: 0.87-1.19, P heterogeneity = 0.97, and I (2) = 0%). CONCLUSION: The GSTM1 null polymorphism may be associated with an increased risk for EC in Asian but not Caucasian populations.