A Comparison of Survival Between Radiosurgery and Stereotactic Implants for Malignant Astrocytomas

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Abstract
The purpose of this paper is to compare the survial of three groups of patients with high grade supratentorial gliomas who were treated on three sequential protocols with surgical resection, external beam fractionated radiotherapy and a boost to the residual contrasting enhancing mass by either interstitial brachytherapy (IB, n = 33), by interstitial thermoradiotherapy (IT, n = 25) or by stereotactic radiosurgery (SRS, n = 19). The primary aim of this study was to evaluate the role of different boosting techniques in the inital management of primary brain tumors. External beam radiotherapy doses were escalated from one study to the next so that the median doses given to the IB, the IT, and the SRS groups were 41.4Gy, 48.4Gy, and 59.4 Gy, respectively. The median dose of interstitial irradiation or stereotactic radiosurgery, were 40 Gy, 32.2 Gy and 10 Gy, respectively, for the same groups. Follow-up was such that all living patients had been followed for a minimum of 30, 27, 4 months in the IB, IT, and SRS groups, respectively; hence, twelve-month survival was 52% (95% CI: 34%–69%), 80% (95% CI: 64%–96%), and 51% (95% CI: 24%–78%) in the same respective groups. Using a multivariate Cox proportional hazards model, treatment with IT conferred a survival advantage over IB (p = 0.029). Furthermore, survival of patients treated with SRS did not significantly differ from that of patients treated with an implant with or without hyperthermia. We conclude that within the constraints of the selection factors and different treatment parameters used in these studies, stereotactic radiosurgery offers the same survival advantage as interstitial implant but with reduced morbidity and mortality. However, interstitial brachytherapy can be combined with hyperthermia and this combined modality approach appears to decrease by half the risk of dying from a malignant glioma when compared with interstitial irradiation alone.