Vestibular schwannomas related to neurofibromatosis type 2 (NF2) are difficult to manage and are sometimes treated with a noninvasive option—stereotactic radiosurgery. A retrospective study conducted by an international, multicentre team and reported in Neurosurgery found that stereotactic radiosurgery is effective for patients with these tumours while preserving serviceable hearing and not causing radiation-related tumour development or malignant transformation.
NF2 is a genetic condition that results in the growth of tumours of the brain, spinal cord, and peripheral nerves. A vestibular schwannoma (also known as acoustic neuroma, acoustic neurinoma, or acoustic neurilemoma) develops from the nerves of the inner ear that control balance and hearing. Many people with NF2 develop vestibular schwannomas in both ears that are very difficult to manage, often requiring multiple surgeries and/or other procedures. Vestibular schwannomas can lead to hearing loss, facial weakness or numbness, and in large tumours, compression of cranial nerves and the brainstem leading to weakness, disequilibrium, difficulty swallowing, and hydrocephalus.
To better understand the effectiveness and safety of stereotactic radiosurgery for NF2-related vestibular schwannomas, Hussam Abou-Al-Shaar (University of Pittsburgh Medical Center, Pittsburgh, USA) and colleagues reviewed data on 267 patients (328 vestibular schwannomas) who underwent single-session stereotactic radiosurgery at 12 centres across the world.
The researchers report multiple positive outcomes:
- Tumour control likelihood of 77% at 10 years and 52% at 15 years
- Likelihood of not requiring additional treatment of 85% at 10 years and 75% at 15 years
- Likelihood of preserving serviceable hearing of 64% at five years and 35% at 10 years.
The only significant predictor of tumour progression was tumour volume, with each 1cm3 increase in tumour volume increasing the relative risk of tumor progression by 8%. The tumour progression rate was 48% at 15 years after stereotactic radiosurgery, but only 25% of patients required additional treatment by that time point, suggesting that despite radiographic progression, only half merited treatment.
Significant predictors of loss of serviceable hearing were older age (3% greater risk per year of age after stereotactic radiosurgery) and presence of bilateral vestibular schwannomas (4.56 times greater risk).
Abou-Al-Shaar and colleagues report that during the median 59 months of follow-up, “we did not observe any event of radiation-induced tumour development or NF2-associated vestibular schwannoma malignant transformation.” This has been a concern in patients with NF2 given their underlying propensity to develop tumours. The authors note that despite the benefits of stereotactic radiosurgery and its good safety profile, its use in patients with NF2 “remains an area of controversy and concern among physicians. We hope that the findings of this study address some of these concerns.”
Abou-Al-Shaar’s group concludes that their results point to the need for early treatment of vestibular schwannoma in patients with NF2. “Tumour volume appeared to significantly impact tumour control and freedom from additional treatment, advocating for early stereotactic radiosurgery to maximise benefits and delay clinical deterioration.”