Chemotherapy treatments, while life-saving, carry a risk of damaging the inner ear, a side effect known as ototoxicity. This damage affects the structures responsible for hearing and balance, potentially leading to permanent hearing loss. The severity depends heavily on the specific drugs used, the total dose administered, and individual patient vulnerabilities like age or pre-existing conditions.
Chemotherapy Drugs That Cause Hearing Damage (Ototoxicity)
The primary culprits behind chemotherapy-induced hearing damage are platinum-based agents, including cisplatin and, to a lesser extent, carboplatin. These drugs are widely used to treat various solid tumors. Cisplatin is particularly potent, with reported rates of hearing loss ranging from 40–60% in adults and up to 70% in children.
The damage occurs because platinum compounds accumulate in the inner ear, specifically targeting the delicate sensory hair cells within the cochlea. These outer hair cells are highly susceptible to the drug’s effects. The damage typically begins at the base of the cochlea, which detects high-frequency sounds, and progresses toward the apex.
The risk of damage is closely tied to the cumulative dose the patient receives. The more total platinum compound administered, the higher the likelihood of developing hearing impairment. Although carboplatin is considered less ototoxic than cisplatin, it can still cause damage, especially in high doses or when used with other ototoxic agents. Other agents, such as certain vinca alkaloids or high-dose methotrexate, also carry an ototoxic risk, though less commonly.
Signs of Chemotherapy-Related Hearing Loss
Chemotherapy-induced hearing loss often manifests in a specific pattern that can be subtle at first. Since the damage affects the high-frequency range (often above 8,000 Hertz), a person may struggle to hear the sharp sounds of consonant speech, such as “s,” “f,” or “th,” which are crucial for clarity.
Patients often notice difficulty understanding conversations, particularly in environments with background noise, even if they can hear the volume of the voices. This inability to discern speech from other sounds results directly from the inner ear damage. The hearing loss is typically bilateral, affecting both ears in a symmetrical pattern.
Another common sign of inner ear damage is tinnitus, which is perceived as ringing, buzzing, or roaring in the ears. Tinnitus can vary in pitch and intensity and may be a temporary side effect or a persistent symptom. In some cases, hearing loss may not be immediately apparent and can progress gradually, or even worsen, after the chemotherapy regimen is completed.
Monitoring and Treating Hearing Changes
Proactive monitoring is the most effective strategy for managing the risk of ototoxicity. This process begins with obtaining a baseline hearing test (audiogram) before the first dose of the ototoxic drug is administered. This initial test provides a reference point against which all subsequent evaluations can be compared to detect minor changes.
Continuous audiological monitoring is recommended throughout the treatment period, often before each chemotherapy cycle, to catch cochlear injury before it progresses into the speech frequency range. These tests frequently include high-frequency audiometry, which is more sensitive to initial drug-induced damage than conventional hearing tests. If a significant change is identified, the medical team may consider adjusting the drug dosage, increasing the interval between treatments, or switching to an alternative drug, provided cancer treatment efficacy is not compromised.
In the pediatric setting, sodium thiosulfate has been approved as an otoprotective agent to reduce the risk of cisplatin-related ototoxicity in children with certain solid tumors. For adults, there is currently no universally approved drug to prevent this damage, though various protective agents are under investigation. If permanent hearing loss occurs, rehabilitation options include hearing aids to amplify sound or, in cases of profound loss, cochlear implants. Patients may also benefit from counseling and communication strategies.