A Systematic Review of Ion Radiotherapy in Maintaining Local Control Regarding Atypical and Anaplastic Meningiomas
William Coggins
University of Texas Medical Branch
Objective: Meningiomas are among the most common primary brain neoplasms. Atypical and anaplastic meningiomas, unlike their benign counterparts, are highly aggressive, locally destructive, and likely to recur following treatment. As a result, these pathologies are difficult to definitively treat with traditional radiotherapy without injuring adjacent brain parenchyma. Ion radiotherapy, however, possesses unique physical properties, and treatment plans employing this modality can be carefully constructed to avoid critical neural structures. The objectives of this systematic review were to evaluate the utilization and efficacy of ion radiotherapy in the treatment of atypical and anaplastic meningiomas. Methods: The authors performed a systematic review of the literature by querying the PubMed and OVID databases, in concordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, to identify and examine literature addressing the efficacy of ion radiotherapy in maintaining long-term local tumor control for patients with atypical or anaplastic meningiomas. The resulting list of studies produced from queries was then refined to focus on literature published in the English language between January 1, 2009 and July 1, 2018. The outcome of interest was rate of local tumor control at five years after ion radiotherapy. Results: Twelve studies were determined to meet inclusion criteria for this systematic review. 11 of the 12 studies were retrospective; 5 papers evaluated proton therapy and 5 evaluated carbon ion radiotherapy while the remaining 2 papers evaluated both modalities. Across the included studies, proton therapy delivered a mean local control rate of 59.62% after 5 years. Carbon ion radiotherapy studies demonstrated local control rates of 95% and 63% at 2 years for grade II and III meningiomas respectively. In contrast, carbon ion radiotherapy studies that failed to differentiate between atypical and anaplastic meningiomas produced a local control rate of 33% at 2 years. Conclusion: The results gleaned in our systematic review establish that proton and carbon ion radiotherapy maintain comparable rates of local control to conventional photon therapy while allowing for more targeted treatment plans that may limit excess radiation damage. While additional prospective trials are needed, ion therapy represents a burgeoning field in the treatment of atypical and anaplastic meningiomas.