[The development of radiation necrosis of the brain after radiation therapy]

Examination by questionnaire of 102 institutions utilizing radiation therapy throughout the country revealed 97 cases of radiation necrosis of the brain, 41 cases of which have received only one course of radiation therapy with either high energy x-rays or 60Co gamma-rays and that have been histologically confirmed for necrosis. The dose fractionation relationship causing necrosis presumed by Strandquvist's diagram proved to be located along the line with the slope of 0.44 from the interception of 9.9 Gy with a single irradiation. Our own experience of brain tumor and cancer of the paranasal sinus told 2 with developed necrosis (incidence, 0.6%) of 325 cases on radiation therapy at a dose of 50-60 Gy and 5 (incidence, 2.0%) of 253 cases on radiation therapy at a dose of more than 60 Gy.