Interstitial irradiation versus interstitial thermoradiotherapy for supratentorial malignant gliomas: A comparative survival analysis

Purpose: To compare the survival of two groups of patients with supratentorial malignant gliomas who were treated on two sequential protocols with either interstitial thermoradiotherapy or with interstitial irradiation without hyperthermia. 1Methods and Materials: Between 1988-1992, patients with anaplastic astrocytoma or glioblastoma multiforme were treated at the University of Arizona on a Phase I/II protocol of interstitial thermoradiotherapy with ferromagnetic seeds. The treatment protocol consisted of debulking surgery, a course of external beam radiotherapy and hyperthermia given immediately before and after brachytherapy. The survival of patients so treated was compared with that of a similar group of patients treated with interstitial brachytherapy alone at the Barrows Neurological Institute between 1982-1990. Results: Twenty-five patients with primary tumors treated at the time of initial presentation with thermoradiotherapy were compared with a control group of 37 patients treated with interstitial brachytherapy alone. All primary 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 ≤ 0.00001) and histology (anaplastic astrocytoma vs. glioblastoma multiforme, p = 0.0017) were the only factors significantly associated with survival in this data set. From the fitted model, the hazard of dying when treated 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 conclude that an interstitial thermoradiotherapy boost confers a statistically significant survival benefit to patients with primary high grade gliomas when compared to interstitial brachytherapy alone.