Children treated for malignancies may be at risk for early- or delayed-onset hearing loss that can affect learning, communication, school performance, social interaction, and overall quality of life. Hearing loss as a late effect of therapy can occur after exposure to platinum compounds (cisplatin and carboplatin) and cranial irradiation. Children are more susceptible to ototoxicity from platinum agents than adults.[1,2] Risk factors associated with hearing loss with platinum agents include the following:
For cisplatin, the risk of significant hearing loss involving the speech frequencies (500-2000 Hz) usually occurs with cumulative doses that exceed 400 mg/m2 in pediatric patients.[1,3] Ototoxicity after platinum chemotherapy can present or worsen years after completion of therapy. In 59 patients who had received cisplatin, 51% of them developed late-onset hearing loss (occurring at least 6 months after the last dose of cisplatin). Radiation to the posterior fossa and the use of hearing aids were associated with late-onset hearing loss.[4,5] Carboplatin used in conventional (nonmyeloablative) dosing is typically not ototoxic. A single study observed ototoxicity after the use of non-stem cell transplant dosing of carboplatin for retinoblastoma, in that 8 children out of 175 developed hearing loss. For seven of the eight children, the onset of the ototoxicity was delayed a median of 3.7 years. Another study evaluating audiological outcomes among 60 retinoblastoma survivors treated with nonmyeloablative systemic carboplatin and vincristine estimated a cumulative incidence of hearing loss of 20.3% at 10 years. Among the ten (17%) patients who developed sustained grade 3 or 4 hearing loss, nine were younger than 6 months at the start of chemotherapy. Younger age at the start of treatment was the only significant predictor of hearing loss; the cumulative incidence of hearing loss was 39% for patients younger than 6 months versus only 8.3% for patients aged 6 months and older (P = .004). With myeloablative dosing, carboplatin may cause significant ototoxicity. For carboplatin, ototoxicity has been reported to occur at cumulative doses exceeding 400 mg/m2.
Cranial radiation therapy, when used as a single modality, results in ototoxicity when cochlear dosage exceeds 32 Gy. Young patient age and presence of a brain tumor and/or hydrocephalus can increase susceptibility to hearing loss. The onset of radiation-associated hearing loss may be gradual, manifesting months to years after exposure. When used concomitantly with cisplatin, radiation therapy can substantially exacerbate the hearing loss associated with platinum chemotherapy.[10,11,12,13] In a report from the Childhood Cancer Survivor Study (CCSS), 5-year survivors were at increased risk of problems with hearing sounds (relative risk [RR], 2.3), tinnitus (RR, 1.7), hearing loss requiring an aid (RR, 4.4), and hearing loss in one or both ears not corrected by a hearing aid (RR, 5.2), compared with siblings. Temporal lobe (>30 Gy) and posterior fossa radiation (>50 Gy but also 30-49.9 Gy) was associated with these outcomes. Exposure to platinum was associated with an increased risk of problems with hearing sounds (RR, 2.1), tinnitus (RR, 2.8), and hearing loss requiring an aid (RR, 4.1).