Emerging strategies for the prediction of behaviour, growth, and treatment response in vestibular schwannoma

Vestibular schwannoma (VS) can present several management challenges for the clinician. Their unpredictable potential for growth creates uncertainty regarding when active treatment should be initiated, and once growth is confirmed which treatment option should be adopted, notably surgery or radiotherapy, and in particular stereotactic radiosurgery (SRS). The obvious benefits of SRS would ideally come with the ability to reliably predict long-term radiosurgery response/failure. Differentiation from temporary post-treatment phenomena such as transient tumour expansion or reactive swelling remains an unmet need. More powerful again would be the pre-treatment identification of which tumours will respond to radiosurgery and which will not. Over the past decade, there has been emerging interest in the development of non-invasive biomarkers, including imaging, for predicting growth and treatment response in VS. Alongside clinical radiographic predictors for VS growth such as extracanalicular tumour location and growth in the first year, studies have shown potential promise for advanced MRI and blood-based biomarkers that capture pathophysiological mechanism behind VS growth. Emerging interest in radiomics-based analyses of routinely acquired MRI, and the use of physiological imaging techniques such as dynamic-contrast enhanced MRI for pre- and post-treatment evaluation of tumour microvasculature and microstructure holds promise for revolutionizing this area. This article explores the current state of identifying VS growth at initial presentation, predicting treatment response to SRS and detecting early treatment failure, and finally the potential for developing more personalized patient selection for drug therapies, including bevacizumab, as well as emerging novel therapeutics for these tumours.