Malignant glioma following radiotherapy for unrelated primary tumors.

Four cases are documented where a glioma was histologically verified in the irradiation field of a previously treated malignancy of a different cell line. Radiation-induced neoplasia in the central nervous system now has been established in the induction of meningioma and sarcoma. The association between therapeutic irradiation and glioma in the reported cases lends to the evidence that a causal relation does exist. This incidence is small and does not detract from the overall benefit of irradiation as a therapeutic modality.