Supplementary Material for: Meta-Analyses of the Effect of CYP1A1 and CYP2D6 Polymorphisms on the Risk of Head and Neck Squamous Cell Carcinoma

Background: CYP1A1 and CYP2D6 are important genes encoding enzymes involved in the metabolism of toxic chemicals and carcinogens. However, inconclusive results for the association between CYP1A1 and CYP2D6 polymorphisms and the risk of head and neck squamous cell carcinoma (HNSCC) have been reported. We conducted a meta-analysis to evaluate the association of CYP1A1 and CYP2D6 polymorphisms with the risk of HNSCC. Methods: A database search yielded 19 relevant studies. 3 polymorphisms were included in the meta-analysis: CYP1A1, CYP2D6*4 and CYP2D6*10. Random or fixed effect models were used in the analysis. Results: The CYP1A1 polymorphism was associated with HNSCC (for m1m1 vs. m1m2: odds ratio (OR) = 1.26, 95% confidence interval (CI) = 1.030-1.542, p_{heterogeneity} = 0.025; for the recessive model: OR = 1.316, 95% CI = 1.065-1.625, p_{heterogeneity} = 0.001). The analysis showed evidence for association between the CYP2D6*4 polymorphism and HNSCC in Asian populations; however, negative results were also observed in other models. A significant association was also observed between CYP2D6*10 polymorphism and HNSCC risk. Conclusions: The current study demonstrates that the CYP1A1 and CYP2D6 polymorphisms are associated with susceptibility to both development and progression of HNSCC.