gms | German Medical Science

Objective: Patients suffering from Neurofibromatosis Type 2 are prone to develop multiple intracranial neoplasms. To date, little is known about the growth dynamics of these tumors. The aim of our study was to investigate a) the median growth rate per year, b) the growth-free intervals, and c) the growth patterns of these tumors.

Method: MR images of the brain from 52 patients (20 male, 32 female) suffering from NF2 were screened for tumors. The median follow-up time was 76.5 months (range 13 - 199 months). Tumor volumes were determined by volumetric extrapolation after segmentation in data sets (iPlan software, BrainLAB, Munich) if the tumors met the following inclusion criteria: contrast enhanced T1-weighted MRI or CT data sets had to be available from at least two investigations and tumors had to be visible on at least two slices. All tumors that had undergone previous treatment, such as radiation, chemotherapy or bevacizumab treatment were excluded from this study. The tumors were divided into four groups: vestibular schwannomas (VS), meningiomas (M), non-vestibular schwannomas (NVS) and tumors of the cerebello-pontine angle that had previously been subjected to surgery (TX).

Results: 188 tumors could be included in the growth analysis: 39 VS, 95 M, 23 NVS, 31 TX. Within 5 years, vestibular schwannomas and meningiomas doubled their size (195.56% ± 338.26% and 203.94% ± 702.34% compared to baseline), whereas non-vestibular schwannomas and pre-operated tumors of the CPA showed relative volumes of 128.24% ± 64.94% and 138,54% ± 269.54%, respectively. The median time to significant tumor progression was 21 months for VS, NVS and TX, and 17 months for M. Overall, saltatory growth with intervals between episodes of expansion was the most common growth pattern (46.85%). 29.37% of tumors showed linear growth, 11.89% grew exponentially. 5.59% of tumors remained stable and 6.29% decreased in size.

Conclusions: Most NF2-associated tumors show saltatory growth. This fact needs to be born in mind when assessing the results of treatment, especially after radiosurgery and chemotherapy. Meningiomas and untreated vestibular schwannomas grow more rapidly and patients harboring these tumors should receive interdisciplinary attention from an early stage on in order to avoid functional deficits. For imaging studies, we suggest an interval of less than 2 years.