Some losses do not begin with complete silence.
They begin with a missing detail. A sound that seems less distinct. A conversation that becomes harder to follow in a crowded room.
For some people undergoing cancer treatment, these subtle changes may be the first signs of ototoxicity, a treatment-related injury to the auditory system that can cause tinnitus and permanent sensorineural hearing loss (Landier, 2016; Callejo et al., 2015).
Because the earliest changes may not immediately interfere with everyday communication, treatment-related hearing loss can remain unnoticed until the damage becomes more extensive (Knight et al., 2005; Landier, 2016).
The First Frequencies to Fade
Platinum-based chemotherapy is widely used in the treatment of several adult and pediatric cancers, but certain platinum agents can damage structures within the inner ear (Brock et al., 2012; Landier, 2016).
This form of hearing loss typically begins in the higher frequencies and may gradually extend toward lower frequencies as cumulative treatment exposure increases (Brock et al., 2012).
The progression from higher to lower frequencies helps explain why early hearing changes may be difficult for patients and families to recognize without structured audiological monitoring (Brock et al., 2012; Brooks and Knight, 2018).
A patient may still hear that someone is speaking while gradually finding it more difficult to distinguish the detail and clarity within speech, particularly in challenging listening environments (Landier, 2016).
In a study involving 67 children and young adults treated with platinum-based chemotherapy, bilateral decreases in hearing were observed in 61% of participants, with a median time to hearing loss of 135 days (Knight et al., 2005).
The same study concluded that conventional toxicity reporting could underestimate both the frequency and clinical significance of treatment-related hearing loss in pediatric patients (Knight et al., 2005).
Why Can the Damage Continue?
The cochlea is the spiral-shaped structure within the inner ear responsible for converting sound vibrations into signals that can be interpreted by the brain (Landier, 2016).
Research has demonstrated that cisplatin can accumulate within the cochlea and remain present for months or years after treatment has ended (Breglio et al., 2017).
While platinum levels decline in many other organs after treatment, the cochlea appears to retain the compound over considerably longer periods (Breglio et al., 2017).
This prolonged retention may help explain why hearing impairment can continue to progress or become apparent after chemotherapy has been completed (Breglio et al., 2017).
Within the inner ear, cisplatin can promote oxidative stress and cellular injury affecting the structures required for normal hearing (Callejo et al., 2015).
The hearing loss associated with this damage is commonly bilateral, progressive, dose-dependent, and irreversible (Callejo et al., 2015).
Higher cumulative exposure, younger age, pre-existing hearing impairment, cranial irradiation, and exposure to additional ototoxic treatments may influence an individual’s risk and the severity of hearing loss (Brock et al., 2012; Landier, 2016).
More Than a Change in Hearing
The effect of fading frequencies extends beyond the results of an audiogram.
In children, hearing is closely connected to speech and language development, learning, academic achievement, and social participation (Knight et al., 2005; Brock et al., 2012).
High-frequency hearing loss may be especially significant during early childhood, when language and communication skills are developing rapidly (Knight et al., 2005).
Even hearing loss that is considered mild from a clinical perspective may have meaningful consequences for a child’s ability to understand speech, participate in the classroom, and communicate with others (Knight et al., 2005; Brock et al., 2012).
For adults, hearing impairment can create difficulties in conversations, professional environments, family relationships, and social settings (Landier, 2016).
Tinnitus and reduced hearing clarity may also add to the physical and emotional burden experienced during and after cancer treatment (Landier, 2016).
The clinical impact of ototoxicity therefore cannot be understood only by measuring how many frequencies have been lost; it must also be considered in relation to the patient’s daily life, developmental stage, and communication needs (Landier, 2016).
Listening Before the Patient Notices
Because treatment-related cochlear damage is frequently permanent, early and systematic monitoring is an important component of care for patients receiving potentially ototoxic therapies (Brock et al., 2012; Brooks and Knight, 2018).
Audiological assessment before treatment establishes a baseline against which later hearing changes can be evaluated (Brooks and Knight, 2018).
Repeated assessments during treatment may help identify threshold changes before the patient or family becomes fully aware of a difference (Brooks and Knight, 2018).
Long-term follow-up is also important because hearing loss may persist, progress, or become more relevant as the communication demands of education, work, and social life change over time (Landier, 2016; Brooks and Knight, 2018).
Early identification does not reverse cochlear damage, but it can support timely clinical evaluation, hearing rehabilitation, educational assistance, and communication strategies when needed (Brooks and Knight, 2018).
From Detection to Protection
For many years, the management of treatment-related hearing loss focused primarily on detecting damage and supporting patients after it had occurred (Landier, 2016).
Research into otoprotective approaches has begun to explore whether hearing can be protected without reducing the anticancer effectiveness of treatment (Brock et al., 2012; Freyer et al., 2017).
In a multicentre phase III trial involving children receiving cisplatin-containing chemotherapy, hearing loss was identified in 28.6% of participants who received sodium thiosulfate compared with 56.4% of participants in the observation group (Freyer et al., 2017).
These findings provided important clinical evidence that reducing treatment-related hearing loss may be possible in appropriately selected pediatric settings, while also emphasizing the need to evaluate otoprotective strategies within the context of each patient’s disease and treatment plan (Freyer et al., 2017).
Continued research is needed to understand which patients face the greatest risk, how auditory damage can be detected earlier, and how hearing can be protected across different cancer populations and treatment settings (Brock et al., 2012; Landier, 2016).
Hearing the Whole Future
The story of treatment-related hearing loss is not simply about sound becoming quieter.
It is about frequencies disappearing one by one, sometimes before anyone realizes what is being lost.
As cancer survival improves, the long-term effects of treatment are becoming an increasingly important part of comprehensive cancer care (Landier, 2016).
Recognizing ototoxicity, integrating hearing assessments into the patient journey, and supporting research into prevention can help protect not only hearing function but also communication, learning, independence, and quality of life (Brock et al., 2012; Landier, 2016).
Because the future after cancer treatment should not only be longer.
It should also remain connected to every voice, conversation, and sound that gives life meaning.
References
Breglio AM, Rusheen AE, Shide ED, et al. Cisplatin is retained in the cochlea indefinitely following chemotherapy. Nature Communications. 2017;8:1654.
Brock PR, Knight KR, Freyer DR, et al. Platinum-induced ototoxicity in children: a consensus review on mechanisms, predisposition, and protection, including a new International Society of Pediatric Oncology Boston ototoxicity scale. Journal of Clinical Oncology. 2012;30(19):2408-2417.
Brooks B, Knight K. Ototoxicity monitoring in children treated with platinum chemotherapy. International Journal of Audiology. 2018;57(Suppl 4):S34-S40.
Callejo A, Sedó-Cabezón L, Juan ID, Llorens J. Cisplatin-Induced Ototoxicity: Effects, Mechanisms and Protection Strategies. Toxics. 2015;3(3):268-293.
Freyer DR, Chen L, Krailo MD, et al. Effects of sodium thiosulfate versus observation on development of cisplatin-induced hearing loss in children with cancer: a multicentre, randomised, controlled, open-label, phase III trial. The Lancet Oncology. 2017;18(1):63-74.
Knight KR, Kraemer DF, Neuwelt EA. Ototoxicity in children receiving platinum chemotherapy: underestimating a commonly occurring toxicity that may influence academic and social development. Journal of Clinical Oncology. 2005;23(34):8588-8596.
Landier W. Ototoxicity and cancer therapy. Cancer. 2016;122(11):1647-1658.