Chemotherapy and tinnitus: cisplatin and beyond

Of all the medications known to damage hearing, cisplatin occupies a distinct category. It is not merely a reported association in pharmacovigilance databases, or a rare idiosyncratic reaction, or a theoretical risk based on cell culture data. Cisplatin is definitively and dose-dependently ototoxic. The hearing loss it causes is usually permanent. And because it is one of the most effective anticancer agents available for certain solid tumors, many patients face a clear trade-off: accept the risk of hearing damage in exchange for the best chance against their cancer.

Understanding cisplatin ototoxicity matters for patients, caregivers, and clinicians involved in oncology care. It also matters for tinnitus specifically, because tinnitus is often the first symptom to appear, sometimes preceding measurable audiometric change.

How cisplatin damages the cochlea

Cisplatin accumulates in the cochlear outer hair cells, particularly in the basal turn of the cochlea, which processes high-frequency sounds. The NIH StatPearls review describes the mechanism as involving reactive oxygen species production, mitochondrial dysfunction, and activation of apoptotic pathways in outer hair cells. These cells, unlike the cells of many tissues, cannot regenerate in mammals.

The characteristic audiometric pattern of cisplatin ototoxicity is bilateral sensorineural hearing loss beginning at the highest frequencies (typically 8000 Hz and above) and progressing downward toward speech frequencies (2000 to 4000 Hz range) with increasing cumulative dose. This high-frequency-first pattern reflects the basal-to-apical gradient of cisplatin accumulation.

Tinnitus often accompanies cisplatin-induced hearing loss and may appear early in treatment, sometimes after the first infusion, before audiometric thresholds in the speech frequencies are affected. For patients who develop tinnitus during chemotherapy, it is an important signal that warrants audiological evaluation.

Risk factors for cisplatin ototoxicity

Several factors increase the likelihood and severity of cisplatin-induced hearing damage:

Cumulative dose. The total amount of cisplatin administered is the strongest predictor of ototoxicity. Each infusion adds to cumulative cochlear exposure. Standard-dose regimens carry lower risk than high-dose regimens, and the relationship is dose-dependent rather than all-or-nothing.

Prior hearing loss. Pre-existing sensorineural hearing loss, from noise exposure, age-related change, or other causes, increases vulnerability. The cochlea has less reserve to absorb further damage.

Age. Both pediatric patients and older adults are at higher risk. Children are disproportionately susceptible, possibly because the developing auditory system is more vulnerable. This has driven much of the research into otoprotection in pediatric oncology.

Concurrent noise exposure. Evidence from animal models suggests that noise exposure during cisplatin treatment potentiates cochlear damage. Clinical implications include advising patients undergoing cisplatin treatment to avoid unnecessary noise exposure.

Renal impairment. Reduced renal clearance of cisplatin increases serum levels and cochlear exposure. Monitoring renal function and dose-adjusting accordingly is standard practice.

Concurrent ototoxic drugs. Aminoglycoside antibiotics and loop diuretics (particularly ethacrynic acid) are additive with cisplatin in cochlear toxicity. These combinations are avoided where possible.

Genetic factors. Variants in the TPMT and ACYP2 genes, among others, have been identified as risk factors for cisplatin ototoxicity in pharmacogenomic studies. Genetic risk stratification is not yet standard clinical practice but is an active research area.

Other ototoxic chemotherapy agents

Cisplatin is the primary concern, but it is not the only chemotherapy agent that can affect hearing.

Carboplatin is considerably less ototoxic at standard doses but causes hearing loss at high doses, particularly in pediatric regimens. The NIDCD includes carboplatin on lists of ototoxic medications.

Oxaliplatin, another platinum compound, has a different toxicity profile focused primarily on peripheral neuropathy rather than ototoxicity, though auditory effects have been reported.

Bleomycin and vinca alkaloids have been associated with auditory symptoms in case reports, but their ototoxic potential is far less established than that of cisplatin.

Monitoring: who, when, and how

The ASHA ototoxicity monitoring guidelines recommend baseline audiological evaluation before starting cisplatin, with serial assessments during and after treatment. The timing of monitoring visits depends on the treatment schedule: patients receiving weekly cisplatin may need more frequent audiological checks than those on longer cycles.

High-frequency audiometry, extending testing to 12,500 or 16,000 Hz, detects early basal-turn changes before they reach the speech frequency range. This extends the warning window, potentially allowing dose adjustment or protocol modification before speech-frequency hearing is compromised.

Distortion product otoacoustic emissions (DPOAEs) can also detect outer hair cell dysfunction and complement audiometry, particularly in patients who cannot perform conventional audiometry reliably.

When audiometric changes are detected, the oncology and audiology teams discuss whether the emerging hearing loss changes the benefit-risk calculus for continuing the current cisplatin dose or schedule. This is a complex decision balancing hearing preservation against cancer outcomes, and it involves the patient directly.

Otoprotection: sodium thiosulfate and beyond

Sodium thiosulfate (STS) administered after cisplatin infusion provides a protective effect by acting as a cisplatin scavenger in peripheral tissues including the cochlea. The timing is critical: STS must be given after cisplatin to avoid neutralizing its antitumor effect.

The SIOPEL 6 randomized trial demonstrated significant hearing protection with intravenous STS in children with hepatoblastoma treated with cisplatin. This led to guideline recommendations for STS use in certain pediatric populations. Whether STS compromises antitumor efficacy in all settings is still under study, and its routine use in adult oncology is not yet standard.

Other otoprotective approaches under investigation include N-acetylcysteine, D-methionine, and various antioxidants. None has yet demonstrated the same level of clinical evidence as STS in pediatric patients.

After treatment: living with ototoxic hearing loss

For patients who complete chemotherapy and have residual hearing loss, conventional audiological management applies: hearing aids for mild to moderate loss, bone-anchored devices where appropriate, and cochlear implantation for severe to profound loss. Auditory rehabilitation can be particularly important for cancer survivors returning to work and social life.

Tinnitus that develops during cisplatin treatment may persist after treatment ends. The NHS UK recommends that cancer survivors with ongoing tinnitus or hearing difficulty seek audiological evaluation, both to characterize the hearing status accurately and to access appropriate support.

If symptoms persist or change, see an audiologist or physician.