Implantable hearing devices following head and neck cancer treatment

Introduction

Hearing loss in patients with head and neck cancers (HNC) is a well-known issue, but hearing rehabilitation in this group is less well studied (1,2). Hearing loss in HNC can be caused by direct involvement of the ear and related structures including the external ear, middle ear, inner ear, or the Eustachian tube. More commonly, hearing loss in HNC is a sequelae of oncologic treatment, including surgery, radiation therapy, and immunotherapy or chemotherapy. The resulting hearing loss can be conductive, sensorineural, or mixed.

Loss of hearing is known to contribute to communication difficulties, leading to significant impacts on a patient’s psychosocial function and quality of life (3). More recently, a number of prominent studies have associated hearing loss in the elderly population with a higher risk of social isolation and loneliness (4-6). It has been hypothesised that this may contribute to why patients with hearing loss may be at a higher risk of poor mental health and cognitive decline (4-6). A large systematic review of 35 studies found that hearing loss in older adults is associated with 1.47-fold greater odds of depression (5). Additionally, a study of 7,135 participants by Myrstad et al. (2023) found that in individuals aged under 85, there was a 36% increased risk [risk ratio (RR) 1.36, 95% confidence interval (CI): 1.11–1.67, P<0.003] of dementia in those with hearing loss compared to without (6). Importantly, hearing rehabilitation using conventional hearing aids has the potential to improve rates of depression and cognitive function among new users (7). This underscores the importance of hearing rehabilitation, especially in patients following HNC treatment. Preliminary studies suggest that cochlear implantation in older adults may be protective against cognitive decline, while studies have observed a positive impact of cochlear implantation on quality of life (8,9).

Cancer survivorship in HNC encompasses the challenges that patients who have been diagnosed with cancer go through, including psychosocial, medical and functional (10). These challenges include the potential impact on hearing and subsequently on quality of life that HNC treatments can have.

Surgical excision and reconstruction can result in significant conductive hearing loss and impact a patient’s ability to use conventional air conduction hearing aids, as they require a pinna to support a device processor, as well as a patent, dry external auditory canal.

Approximately one-third of patients who receive radiotherapy with a field that includes the inner ear experience sensorineural hearing loss due to radiation-related injury of the cochlear and vestibulocochlear nerve (11-13). Radiotherapy of the head and neck also has the potential to cause a conductive hearing loss due to otitis media with effusion, which occurs in 8–29% of patients receiving radiation to this region (14). Furthermore, osteoradionecrosis of the temporal bone is a well-recognised complication of radiotherapy, which has been reported to occur in around 8.5% of patients treated with radiotherapy involving the temporal bone region (15). This can lead to exposed tympanic bone, with resultant chronic otorrhoea, making the use of conventional hearing aids challenging (16). Additionally, chemotherapy agents are known to cause sensorineural hearing loss. Specifically, platinum-based agents such as cisplatin (particularly high-dose regimens) or carboplatin have a strong association with sensorineural hearing loss, with a prevalence in one large meta-analysis of 43.17% (2,17,18).

Previous studies on hearing rehabilitation post HNC treatment were based on patient cohorts following treatment for nasopharyngeal tumours, primary temporal bone tumours as well as posterior fossa intracranial tumours (19-23). There is limited literature regarding hearing rehabilitation in patients following treatment of locally advanced peri-auricular cutaneous tumours. Australia and New Zealand have one of the highest incidences of head and neck non-melanoma skin cancers in the world (24,25). Treatment may include lateral temporal bone resection (LTBR) and adjuvant radiation therapy leading to hearing loss and inability to use conventional hearing amplification devices (26). Furthermore, implantable hearing devices (osseointegrated devices and cochlear implants) in irradiated temporal bones face increased challenges with osseointegration, wound healing and osteoradionecrosis (2,27). This study aims to evaluate the safety, audiologic outcomes, and complication rates of cochlear and osseointegrated hearing implants in patients previously treated with radiotherapy for HNC.

Methods

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. Ethics approval was obtained from the Royal Victorian Eye and Ear Hospital Ethics Committee (No. 18/1367HS/22). Because of the retrospective nature of the research, the requirement for informed consent was waived. A retrospective review of a prospective database for all patients who had implantable hearing devices at the Royal Victorian Eye and Ear Hospital was conducted from 1^st May 2015 until 31^st May 2024. Adult patients who have undergone cochlear implantation or osseointegrated device implantation with a history of previous HNC who received radiotherapy as part of their treatment regimen were included (Figure 1). The study is reported according to the STROBE reporting guidelines (available at https://www.theajo.com/article/view/10.21037/ajo-25-30/rc).

Figure 1 Flow diagram of patient selection.

Speech discrimination testing was conducted pre-operatively for each patient, for both individual ears and binaurally. Post-operatively, testing was performed at three and 12 months using only the implantable hearing device. Monosyllabic words were administered for each listening condition using a pre-recorded list of consonant-nucleus-consonant (CNC) words, presented free-field in quiet, auditory alone at 65 decibels (dB). An Australian male talker was used, and the list of phonemes was balanced according to the rules stipulated by Peterson and Lehiste in 1962 (28). The 12-month results were used for analysis, except for three patients, where the 3-month post-operative data were used as the 12-month results were not recorded (one from the osseointegrated implant cohort and two from the cochlear implant cohort).

Statistical analysis

Patient demographic data, including age and co-morbidities was collected. Data on previous oncologic treatment and pathology, type of implantable hearing device, hearing outcomes as well as short- and long-term complications were collected and analyzed. Categorical variables were presented as frequencies (percentages) while continuous variables were presented as medians and ranges.

Results

Baseline

Medical records were reviewed for 1,462 patients with 1,632 implants, of which 18 met criteria for analysis. Patient demographics, including type of malignancy and treatment is summarised in Table 1.

Osseointegrated implants

All five patients who received osseointegrated implants had initial surgical management of primary (n=2) or metastatic parotid cutaneous squamous cell carcinoma (SCC) (n=3) as well as adjuvant radiotherapy.

Of the five patients who received osseointegrated implants, four received Baha^® Connect implants (Cochlear Limited, Sydney, Australia). One received an Osia implant (OSI200; Cochlear Limited). The median time elapsed from completion of malignancy management to implantation date was 3 years (range, 1–13 years).

Cochlear implantation

Thirteen of the included patients underwent cochlear implantation, of which three had radiotherapy alone, four had chemotherapy and radiotherapy and six had surgery and radiotherapy. Of these six patients who underwent surgery as well as radiotherapy, one had an LTBR, and four had non-ear-related surgery. Two patients had a previous blind sac closure to control otorrhoea from osteoradionecrosis, thus, of the cochlear implant cohort of thirteen, three had an abnormal or no external auditory canal prior to cochlear implantation. The median time following treatment for head and neck malignancy was 22 years (range, 1–38 years).

The cochlear implants consisted of various electrode arrays from the CI500 and CI600 series (Cochlear Limited), and are detailed in Table 1. Post-operative computed tomography (CT) scans showed the electrode array was in the scalar tympani for twelve patients, and unintentionally in the scalar vestibuli for one patient.

Audiologic outcomes

One patient who underwent cochlear implantation and had prior blind sac closure was excluded from the analysis as there was incomplete post-operative audiological data (see Table S1). The median increase in word scores for all patients with available audiological follow-up after cochlear implantation (n=12) was 52.5% (range, 14–66%) and median increase in phoneme scores was 51% (range, 13–86%) (Table 2) (see Table S2 for audiological data). All patients reported subjective hearing improvement in the implanted ear.

Two patients from the osseointegrated device cohort had sufficient data to analyse post-operative hearing outcomes. Both patients found subjective improvement in hearing following implantation and were daily users of the device. Both patients underwent speech perception evaluations, however, testing parameters were not uniform for each patient. However, when comparing device on against device off, both patients indicated significant improvement in at least one speech perception measure.

Complications

One patient experienced infection of the Baha^® Connect surgical site 7 days post-operatively. This patient was 76 years old and had undergone parotidectomy, neck dissection and adjuvant radiotherapy for parotid metastatic cutaneous SCC 13 years prior. Infection around the Baha^® Connect abutment was noted at day seven post-operatively. Subsequently, the abutment was removed and infected tissue was debrided in the operating theatre. The wound healed, and 3 months later, the abutment was replaced without complication.

Two patients experienced intermittent episodes of vertigo following cochlear implantation. One of these patients had a long history of episodic positional vertigo prior to implantation. The other patient experienced nocturnal, episodic positional vertigo. There were no complications related to wound infection or breakdown.

Discussion

HNC treatment, including surgery, radiotherapy and chemotherapy, can have varying, but significant impacts on hearing and quality of life. Our study has demonstrated that cochlear implants and osseointegrated implants can be safely used in patients following HNC surgery and radiotherapy with favourable audiological outcomes.

Audiological outcomes for patients who underwent cochlear implantation in our study were comparable but slightly inferior to results in non-irradiated post-lingual deafness patients. As part of a study at our institution, Morcom et al. (2023) identified a control group of 1,414 patients with mean post-operative CNC word and phoneme scores of 58.1% and 78.8%, respectively, comparable to our results of 51% and 74% for irradiated patients (29). Similarly, in a review of eight patients who received cochlear implantation following radiation for nasopharyngeal carcinoma (NPC), Soh et al. (2012) found the implants to perform to a comparable level to the control group, although a different assessment of hearing outcomes was used and so cannot be directly compared to our study (12).

For patients with HNC who have a predominantly conductive or mixed hearing loss with relatively preserved sensorineural function (bone conduction less than 45 dB), for example, patients who have osteoradionecrosis or middle ear disease after radiotherapy, or patients that have inappropriate anatomy for conventional hearing aids, osseointegrated devices may deliver the most benefit to the patient (30,31). Although it was a small cohort, the osseointegrated cohort experienced subjectively positive outcomes in hearing rehabilitation. Conversely, for HNC patients with sensorineural hearing loss who do not obtain adequate hearing with hearing aids, cochlear implantation may be more appropriate (31).

It is worth noting that the hearing status of the contralateral ear influences the choice of rehabilitation strategy. Local resection and targeted radiotherapy typically result in ipsilateral hearing loss, which may be conductive, sensorineural, or mixed. In contrast, systemic therapies such as chemotherapy can cause ototoxicity leading to bilateral hearing loss (18). In this cohort, none of the patients who received osseointegrated devices received chemotherapy, while 4 out of 13 patients (30.8%) in the cochlear implant group did. It is plausible that these patients also had greater contralateral hearing impairment and decreased sensorineural hearing bilaterally, meaning that placement of an osseointegrated device was not indicated, as it relies on preserved sensorineural hearing on the ipsilateral or contralateral side. Rather, cochlear implantation was more appropriate.

The main complications following osseointegrated hearing aid implantation in HNC patients are related to the effects of radiotherapy on surrounding soft tissues. These include post-operative infections, skin overgrowth, bone exposure and poor osseointegration and its subsequent effect on implant survival (27,32). Of the five patients who underwent osseointegrated implantation, one experienced a significant wound related complication. For the duration of follow-up, no patients underwent complications related to delayed wound breakdown or infection around the abutment. Wilkie et al. (2015) described a 100% osseointegrated implant survival rate for seven patients, however, two suffered from skin flap failure and required revision procedures to achieve adequate surgical site healing (27). However, Nader et al. (2016) reported a higher complication rate in patients who underwent radiation prior to implantation (32). In the non-irradiated group, there were eight complications out of 32 implants (25%), whereas in the irradiated group, there were eight complications out of 19 implants (42%) (32). Our osseointegrated implant cohort had a complication rate of 20%, however, there were only five patients in the cohort. With regards to timing of implantation, all patients underwent implantation at least 1 year following completion of radiotherapy. Notably, the patient who developed post-operative infection had the longest time in the cohort between completion of treatment and implantation. Radiotherapy is known to cause acute and chronic cutaneous reactions, the latter developing years following the completion of treatment, and this may explain the complication seen in this series (33).

Of the 13 patients who underwent cochlear implantation, no complications related to wound breakdown or infection were encountered. Furthermore, no patients required explantation. The only complications encountered were two patients who experienced intermittent episodes of vertigo post-operatively. A meta-analysis by Ahmad et al. (2024) found a complication rate of 6% in the 67 patients who underwent cochlear implantation following radiotherapy for HNC (34). Additionally, in the same meta-analysis including patients who had received radiotherapy for HNC or central nervous system pathology, 3.7% required explantation for dehiscence or infection (34). This rate is higher than the rate of explantation for infection or cutaneous extrusion in studies for the general population (0.5%) (35).

Another consideration prior to implantation of a hearing device following HNC is the patient’s oncological prognosis and the imaging modality required for oncosurveillance. Cochlear implants and osseointegrated hearing devices are safe for CT scans and positron emission tomography scans, however, the devices can cause local artefacts. Recent generations of cochlear implants are magnetic resonance imaging (MRI)-conditional depending on the magnet design (36). Despite this, there is potential for pain around the magnet or even magnet or implant displacement whilst scanning, and there will be an imaging artefact around the implant (36,37). The type of implant, positioning of the receiver/stimulator and timing of implantation as well as its impact on imaging needs to be taken into consideration (38,39). Both clinicians and patients should be aware of these possible effects prior to undergoing cochlear implantation and must weigh up the potential impact on oncosurveillance and likelihood of disease recurrence against the impact that hearing loss is having on the patient’s quality of life. Additionally, an increased duration of deafness may contribute to poorer post-operative hearing outcomes, which again should be taken into consideration when determining timing of implantation (40). Whilst some patients are considered cured of cancer if they remain in remission for 5 years following cancer therapy, this does depend on the type of cancer and treatment received (41,42). Thus, from an oncologic perspective, implantation at this time is generally considered safe, however, a multi-disciplinary discussion between the patient, hearing implant unit and HNC unit may be of benefit. Notably, six patients from the cohort underwent implantation sooner than 5 years following completion of HNC treatment and all remained free of recurrence for the duration of follow-up.

The retrospective nature of the study is a limitation due to the reliance on pre-existing data that is more prone to bias. Additionally, due to the relatively infrequent implantation of patients following HNC treatment, the study is limited by the cohort size. Furthermore, HNC treatment occurs at dedicated HNC centres and therefore medical records were not able to be obtained for HNC treatment details such as radiotherapy fields. With regards to complications, it should be highlighted that all patients who underwent implantation in our cohort were deemed by the operating surgeon to have sufficient skin quality to facilitate adequate wound healing. This is a subjective decision and patients may have been excluded from surgery if it was deemed their skin quality was inadequate to proceed to surgery. Furthermore, four patients were excluded from audiological analysis due to incomplete data. Some of this data may not have been available due to the patients being non-users and hence not engaged in follow-up. Additionally, for three patients, no 12-month post-operative audiograms were available, which similarly could allude to dissatisfaction with hearing outcomes. Hence, our results are prone to potential bias in this way and may overstate the efficacy of the implants.

Conclusions

Hearing loss following HNC treatment can significantly impact a patient’s quality of life. For patients who experience inadequate hearing restoration with conventional amplification devices or are unable to use them, our study has shown that implantable hearing devices can be a safe and effective option for hearing restoration, however, considerations such as the impact on oncosurveillance, position of the receiver and MRI compatibility should be taken into account. Despite the fact that the complication rate is very low, a number of considerations, such as timing after completion of treatment and positioning the implant in a healthy region of soft tissue, should be taken into account.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STROBE reporting checklist. Available at https://www.theajo.com/article/view/10.21037/ajo-25-30/rc

Data Sharing Statement: Available at https://www.theajo.com/article/view/10.21037/ajo-25-30/dss

Peer Review File: Available at https://www.theajo.com/article/view/10.21037/ajo-25-30/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://www.theajo.com/article/view/10.21037/ajo-25-30/coif). T.M. reports that Cochlear Limited provided financial reimbursement for consulting around product development on a sessional basis. There were fewer than five sessions over the last 36 months. The other authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. Ethics approval was obtained from the Royal Victorian Eye and Ear Hospital Ethics Committee (No. 18/1367HS/22). Because of the retrospective nature of the research, the requirement for informed consent was waived.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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