MENINGIOMAS INDUCED BY HIGH-DOSE CRANIAL IRRADIATION

Although meningiomas are known to be induced by low doses of cranial i rradiation, such as those given to treat tinea capitis, little experie nce has been reported on the induction of meningiomas by high-dose cra nial irradiation. The authors describe a series of 10 patients with me ningiomas and a previous history of high-dose radiation therapy, usual ly given for a primary brain tumor. Of the 10 patients, eight were fem ale, three had multiple meningiomas, and the majority had other stigma ta of previous radiation therapy. Eight meningiomas were examined path ologically and one-half were classified as either aggressive or atypic al, or were noted to have a high bromodeoxyuridine labeling index. The average time from radiation therapy to diagnosis of a meningioma was 24 years (range 5 to 40 years), a shorter interval than that previousl y reported for meningiomas induced by lower doses of irradiation. With in this series, patient age at irradiation was significantly correlate d with tumor latency; individuals who were younger at the time of radi ation therapy had a shorter time to meningioma formation. The latency of meningioma formation is therefore influenced by both the radiation dose and the age of the patient at irradiation.