Volumetric growth trends of residual vestibular schwannomas: a systematic review and meta-analysis

Abstract

Background: Gross total resection remains the gold-standard approach for most vestibular schwannomas (VS). In some cases, incomplete resection (IR) becomes a desired alternative to preserve the facial nerve function and the patient’s quality of life. While earlier studies described incompletely resected VSs as dormant, more recent studies reported a higher growth rate following IR. Therefore, examining the volumetric residual VS growth rates could have implications on the follow-up protocols. Moreover, prognostic factors predicting preoperative VS growth have been previously investigated. However, these factors have not been investigated following IR. Our review aims to examine the volumetric growth rate of residual VS following IR and examine variables associated with regrowth.

Methods: The review was conducted in accordance with the PRISMA statement and registered a priori with PROSPERO (CRD42021268113). Six databases were searched from 2010 to 2021. Full-text articles analysing volumetric growth rates in at least 10 patients who had residual VS after IR were assessed. We conducted a meta-analysis using a random-effects model.

Results: 14 studies totalling 849 patients were included in the analysis. The mean planimetric growth rate was 1.57mm/year (range 0.16–3.81 mm/year). The mean volumetric growth rate was 281.725 mm3/year (range 17.9–530.0 mm3/year). Age, sex, pre-operative tumour size/volume, histopathology, MIB-1 index, and Intracanalicular location were not associated with re-growth. Residual tumour size/volume was statistically significant to residual growth (OR = 0.65, 95% CI 0.47–0.90, p-value = 0.01). Radiological re-growth occurred in an average of 26.6% cases (range 0–54.5%).

Conclusion: Only the residual tumour volume/size was associated with residual VS growth. Therefore, postoperative surveillance for at least 5 years remains of utmost importance to monitor disease progression and provide timely interventions. Our study shows that future work should be aimed at molecular and histological characteristics of residual VSs to aid prognostic understanding of residual growth.