The management of malignant gliomas with radiation therapy: Therapeutic results and research strategies

Abstract

I t is estimated that in 1991, 16,700 new cases of primary central nervous system tumors will be diagnosed in the United States, and that 11,500 patients will succumb to their disease.’ Malignant gliomas comprise 33% to 45% of primary brain tumors,2’3 and of these, nearly 85% are glioblastoma multiforme.2’4 The 1980 patterns of care survey for brain tumor patients conducted by the Joint Section on Central Nervous System Tumors of the American Association of Neurological Surgeons and Congress of Neurological Surgeons and the American College of Surgeons Commission on Cancer found that the 5-year survival rate for patients with anaplastic astrocytomas was 18%, while it was only 5% for those with glioblastoma multiforme.* With few exceptions, there has been little improvement in the outcome of patients with malignant gliomas over the past decade. Prospective clinical studies have shown both the efficacy and the shortcomings of conventional radiation therapy in the treatment of malignant gliomas.5,6 The response of these lesions to standard radiotherapeutic techniques is limited by their striking inherent radioresistance’ and the radiosensitivity of the surrounding normal brain tissue.’ In addition to pursuing more effective chemotherapy programs, research strategies have focused on methods designed to enhance the effectiveness of external irradiation using hypoxic cell radiosensitizers, halogenated pyrimidine analogs, and altered fractionation schemes, or to selectively augment the tumor dose using interstitial brachytherapy. Single-institution and cooperative group studies using these approaches are now in progress. This review examines