CNS tumor induction by radiotherapy: a report of four new cases and estimate of dose required.

We have analyzed 60 cases of intra-axial brain tumors associated with antecedent radiation therapy. These include four new cases. The patients had originally received radiation therapy for three reasons: (a) cranial irradiation for acute lymphoblastic leukemia (ALL), (b) definitive treatment of CNS neoplasia, and (c) treatment of benign disease (mostly cutaneous infections). The number of cases reported during the past decade has greatly increased as compared to previous years. Forty-six of the 60 intra-axial tumors have been reported since 1978. The relative risk of induction of an intra-axial brain tumor by radiation therapy is estimated to be more than 100, as compared to individuals who have not had head irradiation.