COMT and cancer: Variants of thiopurine S-methyltransferase TPMT (rs12201199, rs180046 and rs1142345) and catechol O-methyltransferase (COMT) (rs4646316 and rs9332377) were reported to be associated with ototoxicity after treatment with cisplatin in different cancers, including HGOS [123,125].