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Explore this issue:April 2019
A common question by patients with newly diagnosed vestibular schwannomas (VS) is, “Which treatment will best preserve my hearing?” Currently, management of this benign tumor arising from the eighth cranial nerve sheath includes three broad options: observation with serial imaging, microsurgery, and radiotherapy. There are no high-quality, prospective controlled trials comparing outcomes among these three treatment modalities. Therefore, treatment recommendations are largely based on data from single-institution case series. As outcomes of tumor control and facial nerve preservation have improved with modern surgical and radiotherapy techniques, the possibility of hearing preservation (HP) often plays a significant role for patients and physicians making treatment decisions.
The heterogeneity of data poses a major challenge to providing accurate estimates of hearing preservation rates with radiotherapy for VS. Indications for treatment and inclusion criteria vary widely by institution. Radiation may be delivered in a single dose or as many as 30. The radiation source may be cobalt (e.g., GammaKnife surgery [GKS]) or a linear accelerator (e.g., CyberKnife). The methods for reproducing localization differ between techniques as well. Moreover, hearing outcomes are not standardized. For example, some publications simply report the patient’s subjective ability to use the telephone at the first post-treatment visit, whereas other studies utilize audiograms to provide an objective measure of hearing in the treated ear. Traditionally, serviceable hearing has been defined as pure-tone audiometry (PTA) < 50 db with speech discrimination scores (SDS) > 50%, corresponding to American Academy of Otolaryngology–Head and Neck Surgery class A or B, or Garner-Robertson (GR) grade 1 or 2. These differences result in widely varied rates of hearing preservation (between 10% and 90%) after radiotherapy for VS.
The level of evidence of reviewed articles is low. Given that the field involves rapidly developing technology, this is not surprising. Moreover, synthesis of data from case series is vitally important, as controlled studies comparing radiotherapy against microsurgery or conservative management would logistically be very challenging. Evidence from modern, highly conformal, low-dose radiation techniques demonstrate that long-term hearing preservation rates are poor; an approximately 80% hearing preservation rate at two years posttreatment falls to approximately 23% at 10 years. Although radiation therapy provides patients with satisfactory short-term hearing preservation, this treatment modality does not reliably preserve hearing in the long term. It is important when assessing publications in this field to thoroughly scrutinize the methodology, systems of hearing classification, and time to follow-up to provide patients with the most accurate estimations of hearing preservation (Laryngoscope. 2019;129:775–776).