Minimal Effect of Bevacizumab Treatment on Residual Vestibular Schwannomas after Partial Resection in Young Neurofibromatosis Type 2 Patients

Abstract

Hearing-preserving partial resection of neurofibromatosis type 2 (NF2) associated vestibular schwannomas (VS) is a preferred treatment strategy, particularly for children and adolescents. However, the residual tumors do grow and lead at some point to continued hearing deterioration. An adjuvant bevacizumab treatment may provide an option for slowing down this process. In this retrospective study, we reviewed tumor volume and hearing data of 16 operated VS in nine patients younger than 30 years over a period of 63 to 142 months. All these patients had one or more bevacizumab treatment periods and most of them had a non-treatment period after surgery. Four different patterns of growth were observed for the residual tumors: (1) growth in the non-treatment periods, which slowed down in the treatment periods; (2) growth slowed down in one but not in another on-period; (3) unaffected growth; (4) no or minimal growth regardless of the treatment. Neither radiological regression of tumor volume nor hearing improvement were observed in the treatment periods. Accelerated hearing deterioration was observed in several non-treatment periods, but also in some treatment periods. No straightforward correlation can be drawn between tumor growth and hearing scores. Tumor growth and worsening of hearing between two measurement points were slightly less in the treatment periods; however, the differences were not significant, because variations were large. In conclusion, our comprehensive follow-up on 16 VS in nine NF2 patients did show heterogenous effects of bevacizumab on small residual vestibular schwannomas after surgery both regarding tumor size and hearing preservation. Thus, smaller and slower growing tumor residuals seem to behave differently to bevacizumab than reported for not-operated faster growing VS.

Managing NF2-associated vestibular schwannomas in children and young adults: review of an institutional series regarding effects of surgery and bevacizumab on growth rates, tumor volume, and hearing quality

“…Preop, preoperative; Postop, postoperative. This data was illustrated and published in the original work of Gugel et al [26] significance [41]. Third, only 4 studies focused on young NF2 patients with a compatible age range [33,34,38,44] and among them, only one study used volumetry-based calculation for VS growth rate [44].…”

“…The extensive analysis with in depth information on all details and subgroups including supplementary information can be found in the 3 original publications [24][25][26].…”

“…This review paper summarizes our institutional experience with adolescents and young adults with NF2 regarding the VS management, aiming at preservation of a functional hearing as long as possible. We related to and condense the results of three original publications on the topics of growth rate [24], effects of surgery on hearing [25], and effects of second line bevacizumab [26] into one review, to create a comprehensive overview on the topic for the reader. We discuss the results in the light of the recent literature.…”

“…Data availability This work is a summary of three original articles which has been published before (Gugel et al Cancers (Basel). 2019 Nov 25 [26]; Gugel et al J Neurosurg Pediatr. 2019 Aug 23 [24]; Cancers (Basel).…”

Neurofibromatosis

“…One original article found in 16 postoperative patients heterogeneous effects of this treatment with no clear effect in treatment periods compared with periods off treatment. This led the authors to conclude that tumor residuals respond differently to bevacizumab than non-operated faster growing VS [ 8 ]. Further research in therefore clearly needed before recommendations for postoperative bevacizumab can be made.…”