Role of adjuvant radiotherapy in atypical (WHO grade II) and anaplastic (WHO grade III) meningiomas: a systematic review

The systematic adoption of the histopathologic criteria provided by the 2016 update of the WHO classification of brain tumors has markedly increased the relative proportion of atypical and anaplastic meningiomas. These tumors exhibit a much greater recurrence rate compared to benign meningiomas, which negatively impacts survival. In recent years, the publication of numerous retrospective case series, yet no randomized controlled trials, on the impact of radiation therapy in non-benign meningioma, has yielded conflicting evidence. At present, maximum safe resection, including the dural attachment, is the preferred primary treatment modality for all types of meningiomas. Adjuvant radiotherapy is currently recommended for subtotally resected grade II and for all grade III meningiomas. However, in grade II meningiomas achieving complete resection, close radiologic and clinical observation is a feasible option. Despite the great amount of non-benign meningiomas available and eligible for trials, there is a striking lack of prospective studies testing adjuvant therapies against observation for this subset of patients. An updated and systematic literature review is provided on the effectiveness and indications of radiotherapy on grade II and III meningiomas.