Radiation therapy for gliomas

Abstract

Radiotherapy remains one of the cornerstones of treatment of patients with gliomas. Radiationinduced damage to DNA can result in the loss of proliferative capacity of neoplastic cells. In addition to mitotic cell death, it has recently been found that other cellular events can lead to reproductive failure. Apoptosis, or programmed cell death, has been described as a response to radiation in many cell types. Gradually, radiation has been found to cause a great variety of other changes in both normal and neoplastic tissue, ranging from necrosis due to changes in the vasculalure to alterations in gene expression. As radiosurgery becomes more common and the patients have longer survival, investigators are working to understand the responses of brain tissue to radiation. We present several studies related to the effects of radiation on normal brain and gliomas. One paper suggests a mechanism of radiation-induced reproductive failure that is separate from mitotic cell death and apoptosis. Others describe changes in cytokine regulation and receptor density. After irradiation, necrosis of normal tissue can be indistinguishable from recurrence of the tumor with conventional studies. However, functional imaging can differentiate between neoplasm and functional alterations in tissue due to radiation. While much more work must be done in this field, these papers indicate that radiation therapy results in a variety of cellular and molecular alterations. As a result of these chan-ges, they suggest that irradiated brain tissue is functionally and clinically different from untreated brain.