Radiotherapy intensification for atypical and malignant meningiomas: a systematic review

Abstract

The outcomes of non-benign (WHO Grade 2 and 3) meningiomas are suboptimal and radiotherapy (RT) dose intensification strategies have been investigated. The purpose of this review is to report on clinical practice and outcomes with particular attention to RT doses and techniques. The PICO criteria (Population, Intervention, Comparison and Outcomes) were used to frame the research question, directed at outlining the clinical outcomes in patients with G2-3 meningiomas treated with radiotherapy (RT). The same search strategy was run in Embase and MEDLINE and, after deduplication, returned 1807 records. These were manually screened for relevance and 25 were included. Tumour outcomes and toxicities are not uniformly reported in the selected studies since different endpoints and time points have been used by different authors. Many risk factors for worse outcomes are described, the most common being suboptimal RT. This includes no or delayed RT, low doses, older techniques. A positive association between RT dose and progression-free survival (PFS) has been highlighted by analysing the studies in this review (10/25) that report the same endpoint (5y-PFS). This literature review has shown that standard practice RT leads to suboptimal tumour control rates in G2-3 meningiomas, with a significant proportion of disease recurring after a relatively short follow-up. Randomised controlled trials are needed in this setting to define the optimal RT approach. Given the increasing data to suggest a benefit of higher RT doses for high-risk meningiomas, novel RT technologies with highly conformal dose distributions are preferential to achieve optimal target coverage and organs at risk (OARs) sparing.