Meningiomas are the most common intracranial
tumors. Most
meningiomas are WHO grade 1
tumors whereas less than one-quarter of all
meningiomas are classified as atypical (WHO grade 2) and anaplastic (WHO grade 3)
tumors, based on local invasiveness and cellular features of atypia. Surgical resection remains the cornerstone of
meningioma therapy and represents the definitive treatment for the majority of patients; however, grade 2 and grade 3
meningiomas display more aggressive behavior and are difficult to treat. Several retrospective series have shown the efficacy and safety of postoperative adjuvant external beam
radiation therapy (RT) for patients with atypical and anaplastic
meningiomas. More recently, two phase II prospective trials by the
Radiation Therapy Oncology Group (RTOG 0539) and the European Organisation for Research and Treatment of
Cancer (EORTC 2042) have confirmed the potential benefits of fractionated RT for patients with intermediate and high-risk
meningiomas; however, several issues remain a matter of debate. Controversial topics include the timing of
radiation treatment in patients with totally resected atypical
meningiomas, the optimal radiation technique, dose and fractionation, and treatment planning/target delineation. Ongoing randomized trials are evaluating the efficacy of early adjuvant RT over observation in patients undergoing gross total resection.