Abnormal MGMT promoter methylation may contribute to the risk of esophageal cancer: a meta-analysis of cohort studies

This meta-analysis was conducted aiming to evaluate the relationship between abnormal O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation and the risk of esophageal cancer (EC). A range of electronic databases was searched: Web of Science (1945 similar to 2013), the Cochrane Library Database (Issue 12, 2013), MEDLINE (1966 similar to 2013), EMBASE (1980 similar to 2013), CINAHL (1982 similar to 2013), and the Chinese Biomedical Database (CBM) (1982 similar to 2013) without language restrictions. Meta-analysis was performed with the use of the STATA 12.0 software. In the present meta-analysis, 9 clinical cohort studies with a total of 861 EC patients were included. The pooled results revealed that the frequency of MGMT promoter methylation in cancer tissues was significantly higher than in adjacent and normal tissues (cancer tissues vs adjacent tissues, odds ratio (OR)=6.73, 95 % confidence intervals (95 % CI) 4.75 similar to 9.55, P<0.001; cancer tissues vs normal tissues, OR=13.68, 95 % CI 9.47 similar to 19.75, P<0.001, respectively). Subgroup analyses by pathological type, ethnicity, and sample size suggested that abnormal MGMT promoter methylation also exhibited a higher frequency in all these subgroups (all P<0.05). Our findings provide empirical evidence that abnormal MGMT promoter methylation may contribute to the risk of EC. Thus, detection of MGMT promoter methylation may be utilized as a valuable diagnostic marker for EC.