INTRODUCTION: Treatment with bevacizumab achieves both tumour stabilisation or regression and preservation or improvement of hearing. However, the efficacy of bevacizumab varies between patients and within patients. Side effects due to bevacizumab treatment are also common. It would be of value to predict therapeutic response prior to initiating therapy to prevent unnecessary exposure in patients unlikely to benefit. METHODS AND ANALYSIS: We aim to recruit 25 patients with NF2-related schwannomatosis (NF2) with bilateral vestibular schwannomas. Patients will receive an intravenous injection of 37 MBq [89Zr]bevacizumab followed by positron emission tomography (PET)/CT imaging 4 days later. After clinical evaluation at baseline, patients undergo bevacizumab treatment and are followed up at 3 and 6 months. The primary objective is to examine associations between pretreatment [89Zr]bevacizumab uptake on PET/CT and changes in multiple hearing outcomes and radiological characteristics of the target tumour following treatment. Secondary outcome measures include vestibular functioning, patient reported outcome measures, cranial nerve functionality, peripheral neurology, non-target schwannoma response and renal function. Given the explorative nature of the study, associations between PET-derived metrics and clinical and radiological outcomes will be examined without formal hypothesis testing, using generalised estimating equations to account for within-patient correlation. Pairwise associations will be summarised in an association matrix with multiplicity addressed using an all-resolutions inference approach, and findings will be considered hypothesis generating. ETHICS AND DISSEMINATION: This study was submitted via the Clinical Trials Information System reviewed and approved by the Medical Research Ethics Committee Leiden-The Hague-Delft Delft. The study findings will be disseminated through publication in peer-reviewed scientific journals and by presentation at national and international conferences. TRIAL REGISTRATION NUMBER: The trial is registered at ClinicalTrials.gov Protocol Registration and Results System under the registration ID: NCT05685836.

Purpose: To develop automated vestibular schwannoma measurements on contrast-enhanced T1-and T2-weighted MRI scans. Materials and Methods: MRI data from 214 patients in 37 different centers were retrospectively analyzed between 2020 and 2021. Patients with hearing loss (134 positive for vestibular schwannoma [mean age 6 SD, 54 years 6 12; 64 men] and 80 negative for vestibular schwannoma) were randomly assigned to a training and validation set and to an independent test set. A convolutional neural network (CNN) was trained using fivefold cross-validation for two models (T1 and T2). Quantitative analysis, including Dice index, Hausdorff distance, surface-to-surface distance (S2S), and relative volume error, was used to compare the computer and the human delineations. An observer study was performed in which two experienced physicians evaluated both delineations. Results: The T1-weighted model showed state-of-the-art performance, with a mean S2S distance of less than 0.6 mm for the whole tumor and the intrameatal and extrameatal tumor parts. The whole tumor Dice index and Hausdorff distance were 0.92 and 2.1 mm in the independent test set, respectively. T2-weighted images had a mean S2S distance less than 0.6 mm for the whole tumor and the intrameatal and extrameatal tumor parts. The whole tumor Dice index and Hausdorff distance were 0.87 and 1.5 mm in the independent test set. The observer study indicated that the tool was similar to human delineations in 85%–92% of cases. Conclusion: The CNN model detected and delineated vestibular schwannomas accurately on contrast-enhanced T1-and T2-weighted MRI scans and distinguished the clinically relevant difference between intrameatal and extrameatal tumor parts.

Mutations in SDHD and SDHAF2 (both located on chromosome 11) give rise to hereditary paraganglioma almost exclusively after paternal transmission of the mutation, and tumours often show loss of the entire maternal copy of chromosome 11. The 'Hensen' model postulates that a tumour modifier gene located on chromosome 11p15, a region known to harbour a cluster of imprinted genes, is essential to tumour formation.We observed decreased protein expression of the 11p15 candidate genes CDKN1C, SLC22A18 and ZNF215 evaluated in 60 SDHD-mutated tumours compared to normal carotid body tissue and non-SDH mutant tumours. We then created stable knockdown in vitro models, reasoning that the simultaneous knockdown of SDHD and a maternally expressed 11p15 modifier gene would enhance paraganglioma-related cellular characteristics compared to SDHD knockdown alone. Knockdown of SDHD in SNB19 and SHSY5Y cells resulted in the accumulation of succinate, the stabilization of HIF1 protein and a reduction in cell proliferation. Compared to single knockdown of SDHD, knockdown of SDHD together with SLC22A18 or with CDKN1C led to small but significant increases in cell proliferation and resistance to apoptosis, and to a gene expression profile closely related to the known transcriptional profile of SDH-deficient tumours. Of the 60 SDHD tumours investigated, four tumours showing retention of chromosome 11 showed SLC22A18 and CDKN1C expression levels comparable to levels in tumours showing loss of chromosome 11, suggesting loss of protein expression despite chromosomal retention.