Radiation Induced Meningioma: A Single Institution's Experience and Literature Review

Introduction: Radiation induced meningiomas (RIM) occur in patients with prior history of radiation to the craniospinal axis or head and neck region, for the treatment of prior malignancies. These tumors tend to follow a more aggressive natural history with a tendency for progression and recurrence.

Methods: A retrospective analysis of patients that met criteria for RIM among all patients that underwent surgical treatment for meningioma at our institution between 1998 and 2012. Analysis of clinical presentation, treatment, and WHO grading and its effect on disease recurrence was conducted. Prism 6 was used for recurrence free survival analysis and construction of Kaplan Meier graphs.

Results: RIM is a rare entity and was seen in 27 of 821 patients, only 3.3% of all patients who presented to our institution for the surgical treatment of meningioma. Mean age at time of radiation treatment was 15.2 years, mean age at diagnosis was 42.5 years giving a latency of 27.3 years. More than 80% of the RIM were WHO grade 1. RIM is a separate entity from sporadic meningioma (SM), characterized by greater disease recurrence, greater multiplicity, and lack of female preponderance. In addition the recurrence free survival in RIM in our series is not well predicted by the current WHO grading scheme, log rank test P Value: 0.07. To further validate our findings on recurrence, a review of the literature was performed and recurrence survival analysis was conducted on patients from these studies to evaluate the significance of WHO grade and recurrence after surgical treatment. Lack of association was seen between WHO grading scheme and disease recurrence in RIM patients from literature review, that is, at 30 months post-op, 73% of the grade 1 patients were recurrence free, compared with 72% of the grade 2 patients. The log rank test comparing recurrence free survival between WHO grade I and II revealed a p-value of 0.43.

Conclusion: The epidemiologic outcomes of the RIM patients in our series were in accordance with the existing literature. Although most RIM are WHO grade 1, the WHO grading criteria seems to be less reliable in predicting recurrence free survival in RIM.