Hearing loss is a common side effect for individuals diagnosed with cancer. This connection stems from both the cancer itself and the medical treatments used to combat it. Understanding the specific causes is the first step toward effectively managing and mitigating this impact on a patient’s quality of life. The resulting hearing impairment can range from mild difficulty with high-frequency sounds to profound, permanent deafness, often accompanied by tinnitus.
Hearing Loss Caused by Tumor Location
In some cases, the physical presence of a cancerous or non-cancerous tumor can directly interfere with the auditory system, causing hearing loss. Tumors that grow in the head or neck region may cause direct compression or invasion of structures that are responsible for conducting and processing sound. For instance, head and neck cancers can sometimes invade the middle ear or block the Eustachian tube, leading to a conductive hearing loss where sound waves cannot efficiently reach the inner ear.
Acoustic neuromas, now primarily referred to as vestibular schwannomas, are non-cancerous tumors that cause hearing loss by growing on the vestibulocochlear nerve, the main nerve connecting the inner ear to the brain. This nerve is responsible for transmitting both hearing and balance signals, and the slow-growing tumor physically compresses the nerve, typically leading to a progressive, unilateral sensorineural hearing loss. Brain tumors or metastases near the auditory pathway or brainstem can also cause hearing impairment by exerting pressure or disrupting the neurological signals necessary for hearing. The severity of hearing loss from these masses does not always correlate directly with tumor size, but rather with the specific anatomical structures being affected.
Ototoxicity from Cancer Therapies
The most common cause of cancer-related hearing impairment is ototoxicity, which is damage to the inner ear caused by certain medical treatments. Platinum-based chemotherapy agents, such as cisplatin and carboplatin, are recognized for their ototoxic effects, especially in pediatric patients where up to 75% of children receiving cisplatin may experience permanent hearing loss. These drugs accumulate in the cochlea, generating reactive oxygen species. This chemical stress damages and ultimately destroys the sensory hair cells, which convert sound vibrations into electrical signals the brain can interpret.
This chemotherapy-induced hearing loss is typically permanent, affects both ears, and begins with the inability to hear high-frequency sounds, which are processed by the base of the cochlea. As the cumulative dose of the platinum agent increases, the damage can progress to lower frequencies, eventually affecting the range of normal human speech. Furthermore, radiation therapy directed at the head and neck region can also cause ototoxicity by damaging the structures of the inner ear or by causing inflammation and fluid buildup in the middle ear. The risk of significant hearing damage is particularly high when platinum-based chemotherapy is combined with radiation therapy targeting the area near the ear.
Strategies for Monitoring and Preventing Hearing Damage
Managing the risk of hearing loss begins with proactive monitoring. Before starting any potentially ototoxic treatment, a patient should undergo a baseline audiogram, a specialized hearing test that establishes their starting hearing threshold. Throughout the treatment course, regular audiograms are used to monitor for changes in hearing sensitivity, allowing the medical team to identify damage early.
If a change in hearing is detected, the oncology team may consider adjusting the chemotherapy dose or modifying the treatment schedule, though this must be weighed against effective cancer control. In some pediatric cases, a protective agent called sodium thiosulfate (STS) is administered after the cisplatin infusion to reduce the risk of ototoxicity without compromising the chemotherapy’s anti-cancer effect. STS works by inactivating the platinum compound in the inner ear. For patients with established, permanent hearing loss following cancer treatment, conventional hearing aids can amplify sound to improve communication. In cases of severe to profound loss, advanced solutions such as cochlear implants may be considered.