The CYP2D6*10 SNP is relevant to tramadol pharmacokinetics and opioid dose requirement, while SNPs within UGT2B7 (rs7439366), ABAT (rs1641025), and P2RX7 (rs1718125) have demonstrated some level of potential clinical relevance to cancer pain pharmacogenomics in Asian patients. This evidence concerns the gene CYP2D6 and cancer.