In particular, we found that BQ chewers with the MAOA (rs6323) risk G-allele had a significantly synergistic risk of oral and pharyngeal cancers (AOR = 31.15; 95% CI, 13.43–72.27) and OPMD risk (AOR = 12.77; 95% CI, 3.61–45.20) compared to non-BQ chewers with MAOA rs6323 (T-allele). This evidence concerns the gene MAOA and pharynx cancer.