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. 2017 Feb;78(1):2-10.
doi: 10.1055/s-0036-1584231. Epub 2016 May 31.

Low-Dose Gamma Knife Radiosurgery for Vestibular Schwannomas: Tumor Control and Cranial Nerve Function Preservation After 11 Gy

Andrew J Schumacher  1 , Rohan R Lall  2 , Rishi R Lall  3 , Allan Nanney III  2 , Amit Ayer  2 , Samir Sejpal  4 , Benjamin P Liu  5 , Maryanne Marymont  4 , Plato Lee  4 , Bernard R Bendok  2 , John A Kalapurakal  4 , James P Chandler  2
Affiliations

Low-Dose Gamma Knife Radiosurgery for Vestibular Schwannomas: Tumor Control and Cranial Nerve Function Preservation After 11 Gy

Andrew J Schumacher et al. J Neurol Surg B Skull Base. 2017 Feb.

Abstract

Objectives: This study aims to report tumor control rates and cranial nerve function after low dose (11.0 Gy) Gamma knife radiosurgery (GKRS) in patients with vestibular schwannomas.

Methods: A retrospective chart review was performed on 30 consecutive patients with vestibular schwannomas treated from March 2004 to August 2010 with GKRS at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. The marginal dose for all patients was 11.0 Gy prescribed to the 50% isodose line. Median follow-up time was 42 months. The median treatment volume was 0.53 cm3. Hearing data were obtained from audiometry reports before and after radiosurgery.

Results: The actuarial progression free survival (PFS) based on freedom from surgery was 100% at 5 years. PFS based on freedom from persistent growth was 91% at 5 years. One patient experienced tumor progression requiring resection at 87 months. Serviceable hearing, defined as Gardner-Robertson score of I-II, was preserved in 50% of patients. On univariate and multivariate analyses, only higher mean and maximum dose to the cochlea significantly decreased the proportion of patients with serviceable hearing.

Conclusion: Vestibular schwannomas can be treated with low doses (11.0 Gy) of GKRS with good tumor control and cranial nerve preservation.

Keywords: acoustic; neuroma; radiosurgery; vestibular schwannoma.

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Figures

Fig. 1
Fig. 1
(A) Progression free survival based on freedom from intervention, 95% confidence interval, and number of patients at risk are shown. (B) Progression free survival based on freedom from persistent growth, 95% confidence interval, and number of patients at risk are shown. (C) Freedom from tumor enlargement and 95% confidence interval are shown. (D) Percentage of patients with preserved serviceable hearing and 95% confidence interval are shown.
Fig. 2
Fig. 2
Illustrative case: 68-year-old woman found to have a small left canalicular mass on workup for tinnitus. On follow-up the next year, the mass had grown, and the patient had progressive hearing loss. She elected for radiosurgery, and underwent Gamma knife radiosurgery (Elekta Instrument AB Stockholm, Sweden) with a dose of 11.0 Gy to the 50% isodose line. At 5-year follow-up, there was no progression, and the lesion had shrunk approximately 25%. (A) Pretreatment MRI, (B) 5-year follow-up MRI, (C) treatment plan. MRI, magnetic resonance imaging.
See this image and copyright information in PMC

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