INTERSTITIAL IRRADIATION VERSUS INTERSTITIAL THERMORADIOTHERAPY FOR SUPRATENTORIAL MALIGNANT GLIOMAS - A COMPARATIVE SURVIVAL ANALYSIS

Purpose: To compare the survival of two groups of patients with suprat entorial malignant gliomas who were treated on two sequential protocol s with either interstitial thermoradiotherapy or with interstitial irr adiation without hyperthermia. Methods and Materials: Between 1988-199 2, patients with anaplastic astrocytoma or glioblastoma multiforme wer e treated at the University of Arizona on a Phase I/II protocol of int erstitial thermoradiotherapy with ferromagnetic seeds. The treatment p rotocol consisted of debulking surgery, a course of external beam radi otherapy and hyperthermia given immediately before and after brachythe rapy. The survival of patients so treated was compared with that of a similar group of patients treated with interstitial brachytherapy alon e at the Barrows Neurological Institute between 1982-1990. Results: Tw enty-five patients with primary tumors treated at the time of initial presentation with thermoradiotherapy were compared with a control grou p of 37 patients treated with interstitial brachytherapy alone. All pr imary patients were followed for a minimum of 34 months post implant. Multivariate analysis based on proportional hazards models showed that hyperthermia (p = 0.027), patient age (p less than or equal to 0.0000 1) and histology (anaplastic astrocytoma vs. glioblastoma multiforme, p = 0.0017) were the only factors significantly associated with surviv al in this data set. From the fitted model, the hazard of dying when t reated with hyperthermia was .53 times (95% confidence intervals 0.29- 0.94) than that of the control group. In addition, we treated a small group of patients with recurrent tumors (13 with brachytherapy alone, and eight with thermoradiotherapy) and found no survival difference (p = 0.62). Conclusion: Within the constraints of the selection factors and the different treatment parameters used in these studies, we concl ude that an interstitial thermoradiotherapy boost confers a statistica lly significant survival benefit to patients with primary high grade g liomas when compared to interstitial brachytherapy alone.