Purpose: To describe the whole-body magnetic resonance (WB-MRI) features of peripheral schwannomas in patients with NF2-related schwannomatosis (SWN) treated with bevacizumab for target progressive/symptomatic vestibular schwannomas (VSs).
Methods: In this multi-institution, open-label phase II clinical trial, WB-MRI at 3.0T was performed at baseline, 25-weeks, and 49-weeks after treatment with bevacizumab using STIR, DWI/ADC mapping, pre- and post-contrast T1-weighted imaging. Two readers recorded size and signal characteristics of non-target peripheral lesions (maximum 5 lesions per patient (each from a different body region)). 2D-area (product of two perpendicular measurements), inter-reader reliability and percent change (baseline-49 weeks) was calculated. Radiological response was defined as complete response (CR, disappearance), partial response (PR, > 20% decrease), progressive disease (PD, > 20% increase), and stable disease (SD).
Results: Baseline WB-MRI detected 119 non-target peripheral schwannomas (median:8; range:0-37). Thirty-three peripheral schwannomas in 11 patients (median age (years): 30(range:14-79)) were characterized. Median size(mm) at baseline, 25-weeks, and 49-weeks was 26 (range: 10-88), 26 (range: 10-86), and 25 (range: 9-86), respectively. Lesions were measured with high inter-reader reliability (ICC range 0.990-0.997). Based on largest lesion diameter, all non-target lesions were stable at 49-weeks. Based on 2D-area, the majority of the lesions were SD (31/33 (94%) followed by PR (1/33;3%) and PD (1/33; 3%). There was no change in ADC values or other signal characteristics at 49-weeks.
Conclusions: In NF2-related SWN, WB-MRI enables detection and characterization of peripheral non-target schwannomas as small as 10 mm with high-inter reader reliability. Despite histological similarities to central VSs (targeted for progression), non-target peripheral schwannomas predominantly remained stable on bevacizumab.
Surgical management remains the mainstay of treatment for peripheral schwannomas in patients with NF2-related schwannomatosis (SWN). There is paucity of data on the response of non-vestibular schwannomas (VS) central lesions to systemic treatment and no data on the response of peripheral schwannomas to bevacizumab. In this study, 119 non-target peripheral schwannomas were detected on baseline WB-MRI with a median number of 8 non-target peripheral lesions per patient (range: 0–37), most commonly located in the lower extremities with median largest lesion diameter of 26 mm (range: 10–88 mm). On serial WB-MRI exams after bevacizumab treatment, the majority (94%) of peripheral schwannomas remained stable in size, signal characteristics, ADC values and enhancement pattern.
1. Whole Body MRI enables efficient assessment of non-target peripheral lesions to systemic therapy in patients with schwannomatosis. 2. Despite histological similarities to progressive/symptomatic central vestibular schwannomas targeted for treatment; non-target peripheral schwannomas remain unchanged on WB-MRI in patients with NF2-related SWN on systemic bevacizumab.
Keywords: NF2-related schwannomatosis; Bevacizumab, whole body MRI; Diffusion weighted imaging; Neurofibromatosis type 2; Schwannoma.
© 2025. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.