Does adjuvant external-beam radiotherapy improve outcomes for nonbenign meningiomas? A Surveillance, Epidemiology, and End Results (SEER)-based analysis

Object: The aim of this study was to examine the effect of postoperative external-beam radiation therapy (EBRT) on disease-specific survival in patients with nonbenign meningiomas. Methods: The Surveillance, Epidemiology, and End Results (SEER) database from 1988 to 2007 was queried for cases of resected Grades II (atypical) and III (malignant) meningioma. Disease-specific survival outcomes were determined using Kaplan-Meier survival analysis and Cox proportional hazards models. Logistic regression analysis was used to determine the likelihood of receiving EBRT for Grade II versus Grade III. Because atypical and malignant meningiomas underwent WHO reclassification in 2000, the authors carried out an additional analysis of outcomes of these tumors from 2000 to 2008. Results: There were 657 patients included in the analysis; of these, 244 received adjuvant radiation. Compared with patients with Grade II meningioma, patients with Grade III disease were 41.9% more likely to receive EBRT after gross-total resection and 36.7% more likely to receive it after subtotal resection (95% CI 0.58-3.26). Controlling for grade, extent of resection, size and anatomical location of the tumor, year of diagnosis, race, age, and sex, adjuvant EBRT did not impart a survival benefit (HR 1.492; 95% CI 0.827-2.692). There was also no survival advantage to EBRT in an analysis of cases diagnosed after the WHO 2000 reclassification of meningiomas (HR 0.828; 95% CI 0.350-1.961). Conclusions: The results of this population-based retrospective analysis demonstrate that the role of radiation remains unclear. They underscore the need for randomized prospective clinical trials to assess the usefulness of adjuvant EBRT in Grades II and III meningioma so as to define more precisely the subset of patients who may benefit from the addition of adjuvant radiation.