Compared to the healthy control group (COMT (rs9606186) C/C+G/C genotype), BQ chewers with the COMT rs9606186) risk G/G was significantly related to the risks of oral cavity and pharynx cancers (AOR = 22.13, 95% CI = 10.23–47.84), and the risk of OPMD (AOR = 20.73, 95% CI = 4.97–86.52). This evidence concerns the gene COMT and oculopharyngeal muscular dystrophy.