Radiation-induced meningiomas after high-dose cranial irradiation.

Radiation-induced meningiomas (RIM) are known to occur after high and low dose cranial radiation therapy. Currently, RIM are the most common form of radiation-induced neoplasm reported. We present the largest series of RIM induced by high dose radiation reported thus far and review the literature. Radiation therapy was most commonly given for childhood malignancy. We compared our group of 26 patients with RIM with previously published reports of RIM, and also with 364 patients with spontaneous meningioma (SM) treated at The Royal Melbourne Hospital between 2007 and 2011 with regard to age, gender, and histopathology. In our group of patients with RIM, the mean age at presentation was 38.5 years, in comparison to 60.1 years for patients with SM. The female-to-male ratio was 1.88:1 in RIM compared to 2.37:1 for SM. Of the RIM, 86.5% were World Health Organization (WHO) grade I and 11.5% were grade II (atypical) meningiomas. There were no anaplastic or malignant RIM. Of the SM, 91.5% were WHO grade I, 7.1% WHO grade II, and 1.4% WHO grade III meningiomas. The characteristics of RIM induced by low dose radiation therapy have been well described. It is timely to consider RIM due to high dose radiation, which is now frequently employed in the management of various childhood and other malignancies.