Meningioma after radiotherapy for malignancy

• Radiation-induced meningioma is a known long-term complication of radiation exposure.
• WHO grade I radiation-induced meningiomas demonstrate higher rates of proliferation than sporadic meningioma.
• Higher rates of proliferation and grade II meningioma in this cohort suggest this is different from sporadic meningioma.
• WHO grade I radiation-induced meningiomas require further prospective study.

Complications of radiation exposure have gained importance with increasing cancer survivorship. Secondary malignancies have been associated with cranial radiation exposure. We present our experience with intracranial radiation-induced meningioma (RIM) and discuss the implications of its presentation and natural history for patient management. Patients diagnosed with meningioma who had received radiation therapy between 1960 and 2014 were identified. Records were retrospectively reviewed for details of radiation exposure, previous malignancies, meningioma subtypes, multiplicity and pathologic descriptions, treatment and follow-up. Thirty patients were diagnosed with RIM. Initial malignancies included acute lymphocytic leukemia (33.3%), medulloblastoma (26.7%) and glioma (16.7%) at a mean age of 8.1 years (range 0.04–33 years). The mean radiation dose was 34 Gy (range 16–60 Gy) and latency time to meningioma was 26 years (range 8–51 years). Twenty-one patients (70%) underwent surgery. Of these, 57.1% of tumors were World Health Organization (WHO) grade I while 42.9% were WHO II (atypical). The mean MIB-1 labeling index for patients with WHO I tumors was 5.44%, with 33.3% exhibiting at least 5% staining. Mean follow-up after meningioma diagnosis was 5.8 years. Mortality was zero during the follow-up period. Meningioma is an important long-term complication of therapeutic radiation. While more aggressive pathology occurs more frequently in RIM than in sporadic meningioma, it remains unclear whether this translates into an effect on survival. Further study should be aimed at delineating the risks and benefits of routine surveillance for the development of secondary neoplasms after radiation therapy.