Secondary intracranial meningiomas after high-dose cranial irradiation: report of five cases and review of the literature.

PURPOSE: To review cases of secondary intracranial meningiomas following high-dose cranial irradiation (>/= 10 Gy) identified in Slovenia between 1968 and 1998, to determine their histological profile and to review the literature on this topic. METHODS AND MATERIALS: Personal files of patients treated for secondary intracranial meningioma during a 31-year period were reviewed. In cases which met the criteria for radiation-induced tumors, steroid hormone receptor and Ki-67 status were analyzed. For the literature review, computerized database systems and reference lists from respective publications were used.
RESULTS: Five patients (2 females, 3 males), 3-11 years old at the time of cranial irradiation, developed secondary meningioma after a latency period of 9.5-31.5 years. Three patients had multiple tumors and 2 developed recurrent disease. Of 9 histologically examined tumors, 5 were graded as benign and 4 as atypical meningiomas, with Ki-67 proliferative index 3.2 +/- 3.6 and 10 +/- 6, respectively. The ratio between positive and negative meningiomas regarding immunostaining for progesterone and estrogen receptors was eight-to-one and six-to-three, respectively. Cumulative actuarial risk of secondary meningioma in a cohort of 445 children 16 years or younger treated with high-dose cranial irradiation between 1968 and 1990 in Slovenia at 10, 20, and 25 years was 0.53%, 1.2%, and 8.18%, respectively. Out of 126 cases of radiation-induced meningiomas reported, 57% were females and 43% were males, with mean age at presentation 33 +/- 17.3 years. The majority (68%) of patients was irradiated during childhood. The latency period was significantly shorter in those who aged 5 years or less at the time of cranial irradiation (p = 0.04), and in those with atypical/anaplastic tumor (p = 0.01). Correlation between radiation dose and latency period could not be found.
CONCLUSION: Secondary meningiomas following high-dose cranial irradiation are characterized by younger age at presentation, by higher male-to-female ratio and by biologically more aggressive variants compared to primary spontaneous meningiomas. Latency period correlated with the age at the time of cranial irradiation and with tumor grade but not with irradiation dose. Ki-67 immunoreactivity correlated with histological grade. The progesterone and estrogen receptor immunoreactivity was high. The risk for development of secondary meningioma after high-dose cranial irradiation was increasing with the time of follow-up.