MRI Monitoring of Residual Vestibular Schwannomas: Modeling and Predictors of Growth.

Abstract

The aim was to model residual Vestibular Schwannoma (VS) over time to identify prognostic factors of postsurgical growth. Multicenter retrospective study. Tertiary referral centers. A group of 135 patients who underwent incomplete resection for VS between January 2010 and December 2018. On magnetic resonance imaging (MRI) examinations at baseline (1 year after surgery), patients included were divided into two groups: near-total resection (NTR, <25 mm × 2 mm) and subtotal resection (STR, greater volume). Monitoring of residual VS volume. 3D volumetric segmentation of residual tumors was performed on every MRI examination at baseline and during follow-up to model volume changes over time using the Lambda-Mu-Sigma method. The study followed-up 127 patients (median age: 56 yr) over a median follow-up of 39 months. Most VS residues (76.7%; 89/116) showed no growth at 5 years. Only 27 (23.3%) residues showed signs of regrowth (increase in volume >0.05 cm). The extent of resection is a predictor of tumor growth (odds ratio [OR] = 4.85; for STR over NTR; p = 0.003), but the growth rate was significantly different between STR and NTR residues (p < 0.001). At first, over 2 years after surgery, STR residues decreased (-1.0% volume per year), whereas NTR ones grew (+8% per year). Then, both residues showed sign of regrowth. Postoperative recommendations should now include the natural history of VS residue after resection: even though the growth rate differs between STR and NTR residues, most VS residues showed no growth.