Long-term growth rate of vestibular schwannoma in neurofibromatosis 2: A volumetric consideration.

ABSTRACT

OBJECTIVES/HYPOTHESIS: To determine the long-term growth rate of vestibular schwannoma (VS) in neurofibromatosis type 2 (NF2) patients based on volumetric measurements. STUDY DESIGN: Retrospective review. METHODS: We retrospectively reviewed magnetic resonance imaging (MRI) scans acquired from patients with NF2 from 1999 to 2013. Patients with an annual radiologic follow-up over at least 3 consecutive years were included. Volumetric VS growth was prospectively measured using a three-dimensional imaging workstation and through manual contouring of the lesion. Time to tumor progression was assessed according to the Response Evaluation in Neurofibromatosis and Schwannomatosis Tumor Measurement Group. RESULTS: Eighteen patients presenting with a total of 26 VSs were included. The mean age at diagnosis was 26.1 years (range, 7 to 49 years). One hundred five MRI scans were analyzed during a median radiological follow-up of 5.6 years (range, 3 to 12 years). The annual volume and diameter growth rates were respectively 218.3 mm(3) /yr (range, -10 to 1,250 mm(3) /yr) and 0.9 mm/yr (range, -0.5 to 4.5 mm/yr). Time to tumor progression was 3 years (median survival). There was a weak correlation between volumetric and linear measurements (P < .0001, linear regression, n = 26, r(2) = 0.58). Among the 26 VSs, 76.9% (20/26) showed progression (VS growth more than 20%), 19.2% were stable, and 3.9% (1/26) exhibited shrinkage (spontaneous regression of more than 20% of the initial volume). CONCLUSIONS: This study helps to assess the long-term growth profile of VS in a population of NF2 patients with untreated VS. These data could help to better acknowledge VS natural growth history. LEVEL OF EVIDENCE 4 Laryngoscope, 1262358-2362, 2016.