Serum vitamin E level in esophageal cancer patients: a meta-analysis

Objective To explore the association between esophageal cancer and serum vitamin E level and to provide evidences for researches and prevention of esophageal cancer.Methods Case-control studies on esophageal cancer and serum vitamin E level published from January 1980 to December 2015 were searched through China National Knowledge Infrastructure,Wanfang Database,PubMed,and Web of Science.Meta-analysis was performed with Stata 12.0.Results A total of 9 literatures (7 in Chinese and 2 in English),involving in 358 esophageal cancer cases and 538 controls,were included in the meta-analysis.The meta-analysis showed that the serum vitamin E level of esophageal cancer cases was lower than that of the controls (standardized mean differenceSMD=-0.50,95% confidence interval95%CI=-0.65-0.36,P<0.001).Subgroup analysis found that the serum vitamin E levels of the esophageal cancer cases were lower than those of the controls for the studies conducted in China (SMD=-0.50,95%CI=-0.67-0.33) and in United States (SMD=-0.51,95%CI=-0.77-0.25),with the controls selected from communities (SMD=-0.54,95%CI=-0.69-0.39),with the sample size of larger than 50 (SMD=-0.56,95%CI=-0.71-0.41),with age-matched controls (SMD=-0.57,95%CI=-0.72-0.42),and with serum vitamin E level detection using high performance liquid chromatography (HPLC)(SMD=-0.41,95%CI=-0.59-0.24)and using method other than HPLC (SMD=-0.67,95%CI=-0.91-0.43)(all P<0.001).Sensitivity analysis and publication bias test showed that the results of the study were stable and there was no publication bias for the literatures included in the study.Conclusion Serum vitamin E level is low in esophageal cancer patients.