In HNSCC, genetic polymorphisms in CYP2C19 (e.g., CYP2C192) have been associated with a markedly increased risk of cancer development (OR = 3.36) and reduced therapeutic efficacy of chemotherapeutic agents like cisplatin and 5-fluorouracil, due to altered drug metabolism (Rawal, et al., 2015; Yadav, et al., 2008). This evidence concerns the gene CYP2C19 and cancer.