MATERIALS AND METHODS: A meta-analysis was conducted on published original studies retrieved from the literature using a bibliographic search from two electronic databases: MEDLINE (National library of medicine, USA) and EMBASE. The pooled odds ratio and presence of publication bias in those studies were evaluated.

RESULTS: A total of 49 studies concerning oral cancer (OC) were identified for GSTM1 null genotype. Similarly, 36 studies were identified for GSTT1 null genotype. The pooled OR was 1.551(95% confidence interval [CI]: 1.355-1.774) for the GSTM1 null genotype, while for GSTT1 null genotype, the pooled OR was 1.377 (95% CI: 1.155-1.642). No evidence of publication bias was detected among the included studies.