Irradiation of meningioma: A prototype circumscribed tumor for planning high-dose irradiation of the brain

Abstract

The purpose of this report is to provide specific data concerning the radiation dose required to destroy meningioma, and to demonstrate that radiation doses much greater than the alleged tolerance dose, can be administered to the brain in some patients. Most meningiomas are not responsive to irradiation, but, some surgically incurable lesions benefit from irradiation with radically high doses to small volumes of tissue. The arrest of 7 of 12 consecutive meningiomas in adults for periods of 2–17 years following maximum tumor doses up to 8800 R in 40 days is reported in this paper. All patients, when irradiated, had active tumor in the form of inoperable primary tumor, recurrence or known postoperative residual tumor. Three of the successful results were achieved with orthovoltage radiation. The incidence of brain damage may be acceptable to the patient when it is related to arrest of tumor growth but he must be forewarned of possible brain damage. The factors influencing the radioresponsiveness of meningioma are: the required tumor lethal dose, histology and vascularity of the tumor, anatomical site in the brain, treatment technique for each tumor site, small size of the treated volume, growth rate of the tumor, displacement of normal brain tissue by tumor, inherent individual variations of tumor and normal tissues, quality of the radiation, and tolerance of normal brain tissues. The role of these factors is discussed in the light of modern radiobiological concepts.