Radiation Necrosis

1) The 5 cases were illustrated as typical severe necrosis of the tumors undoubtedly attributable to the irradiation, found in the course of studying the effect of radiation therapy in 84 autopsy cases of intracranial tumors including 59 gliomas. In two cases of craniopharyngoima and of pineal teratoblastoma (biopsied previously), massive, hyalinous, scar-like connective tissue without residual tumor cells was present either on the wall or within the 3rd ventricle. In the case with craniopharyngioma, marked coagulation necrosis was present in the white matter of the right temporal lobe without compressing or dislocating surrounding tissue, conceivably a radiation necrosis of the white matter itself. The 3rd case was of anaplastic glioma (biopsied previously) which showed a focus of extensive coagulation necrosis at the portion corresponding to the left thalamus with small number of residual tumor cells in its marginal zone. The necrotic lesion was so extensive that the surrounding structures were compressed and dislocated. Under the clinical diagnosis of glioma, the 4th and 5th cases had received irradiation but not any operative treatment. Extensive and massive zones of coagulation necrosis were present in the cerebrum (Case 4) and brainstem (Case 4, 5), compressing and dislocating adjacent structures. In both cases no identical glioma cells were observed. However, the morphological findings of the voluminous necrotic lesion similar to that of case 3 allowed us to conclude that the gliomas in cases 4 and 5 had been led to complete coagulation necrosis by irradiation. 2) On the basis of morphological findings of the 84 autopsy cases including abovementioned 5 cases, dose-time relationship in radiation necrosis was discussed. However, any conclusive data were not obtained for the appropriate dose and terms of irradiation which cause necrosis only in tumor tissue without radiation necrosis in surrounding brain tissue. At the end of this discussion, it was suggested that the safety zone for preventing normal brain tissue from causing radiation necrosis would be lower than that of Lindgrens disgram.