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A widely used chemotherapy that can damage hearing, more so in children. Its US label mentions TPMT as a possible factor but says the link has not held up consistently.
Cisplatin, a chemotherapy used in adults and children, is the other common medicine that damages the inner ear. Its US label estimates hearing loss in 40 to 60% of children who receive it and asks for a hearing test before each dose. It says variants in the TPMT gene may contribute, but that the link has not been consistent across populations and studies, so here the hearing tests, not a gene test, are what protect a child.
US prescribing information for cisplatin injection (Fresenius Kabi), revised March 2017: Boxed Warning, Warnings and Adverse Reactions (Ototoxicity). This is the label itself, not a CPIC guideline.
The share of people who carry at least one copy of each version. For the same medicine, it often differs more than tenfold between groups.
TPMT *3C rs1142345 — a non-working version of the enzyme
Worked out from each group's allele frequency: Korean from the Korean studies published in dbSNP, the rest from gnomAD's ancestry groups (via Ensembl), as the survey defines them, not races. How common a version is in a group says nothing about any one person; only a test does.
Cisplatin is a platinum chemotherapy used for many cancers in adults and children. One of its known harms is damage to the inner ear, which shows up as ringing in the ears or loss of high-pitched hearing.
Its US label estimates hearing loss in 40 to 60% of children who receive it, and says it can be worse in children under 5. That is why every child on cisplatin has a hearing test before starting, before each dose, and for several years afterwards.
The label says genetic factors, such as variants in the TPMT gene, may contribute to cisplatin hearing loss, but that the link has not been consistent across populations and studies. TPMT matters much more clearly for the thiopurine medicines.
The label does not ask for it. What it does ask for, for every child, is regular hearing tests, so that hearing loss is caught early.
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Cisplatin. MyGeneLog™. https://www.mygenelog.com/drugs/cisplatin