CYP2C19 and head and neck cancer: Moreover, poor metabolizer genotypes were found to be associated with the increased risks in many cancers, such as esophagus cancer, gastric cancer, lung cancer, head neck cancer, and hepatocellular carcinoma, suggesting the CYP2C19*2 and CYP2C19*3 most likely contributes to cancer susceptibility, particularly in the Asian populations (Wang et al., 2013).