Abstract
We reviewed our experience in managing of NF2-associated vestibular schwannoma (VS) in children and young adults regarding the effect of surgery and postoperative bevacizumab treatment. A total of 579 volumetric and hearing data sets were analyzed. The effect of surgery on tumor volume and growth rate was investigated in 46 tumors and on hearing function in 39 tumors. Long-term hearing follow-up behavior was compared with 20 non-operated ears in additional 15 patients. Sixteen operated VS were treated with bevacizumab. Mutation analysis of the NF2 gene was performed in 25 patients. Surgery significantly slowed down VS growth rate. Factors associated with a higher growth rate were increasing patient age, tumor volume, and constitutional truncating mutations. Immediately after surgery, functional hearing was maintained in 82% of ears. Deterioration of hearing was associated with initial hearing quality, larger tumor volumes, and larger resection amounts. Average hearing scores were initially better in the group of non-operated VS. Over time, hearing scores in both groups worsened with a similar dynamic. During bevacizumab treatment of residual tumors, four different patterns of growth were observed. Decompression of the internal auditory canal with various degrees of tumor resection decreases the postoperative tumor growth rates. Carefully tailored BAEP-guided surgery does not cause additional hearing deterioration. Secondary bevacizumab treatment showed heterogenous effects both regarding tumor size and hearing preservation. It seems that postoperative tumor residuals, that grow slower, behave differently to bevacizumab than reported for not-operated faster growing VS.
Highlights
Neurofibromatosis type 2 (NF2) is an autosomal-dominant disorder caused by inactivation of the NF2 gene on 22q12 resulting in the functional loss of its protein product merlin [1]
Children and young adults with NF2 are extremely dependent on hearing preservation for as long as possible to enable their continuation of social development and education
Under consideration of functional preservation of hearing, early diagnosis of the disease and monitoring of these tumors and their growth rate by 3D tumor volumetry seems very important to be informed of changes “online” and not taken by surprise
Summary
Neurofibromatosis type 2 (NF2) is an autosomal-dominant disorder caused by inactivation of the NF2 gene on 22q12 resulting in the functional loss of its protein product merlin (moesin-ezrin-radixin-like protein) [1]. Different to sporadic VS, NF2-associated VS (NF2-VS) are more likely to become symptomatic in children and young adults [6]. Known growth data from sporadic VS [7] cannot be transferred directly to NF2-VS because of a known higher proliferation index [8, 9], less vascularization, and a more lobular profile [10]. Hearing-preserving treatment strategies are predominantly microsurgery [14] and chemotherapy, e.g., with the vascular endothelial growth factor (VEGF) inhibitor bevacizumab [15, 16]. The use of radiotherapy mostly in form of radiosurgery remains controversial in NF2 [17]
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