Dose-Escalated Conformal Radiotherapy of Glioblastomas – Results of a Retrospective Comparison Applying Radiation Doses of 60 and 70 Gy

Abstract

Dose escalated three-dimensional conformal radiotherapy with 70 Gy against glioblastomas was compared retrospectively with the standard scheme of 60 Gy using 2-D-planning.In the period from 1994 to 1998, a series of 135 patients with glioblastomas was treated by surgery and postoperative radiotherapy. A conversion from 2-D into 3-D-planning was carried out in 4/1996. The prescribed total dose for the first 65 patients was 60 Gy (group 60). A boost up to 70 Gy was added for the remaining 70 patients (group 70).The median survival time was 8.0 months for group 60 and 8.3 months for group 70. A dependency on the applied dose range was found. The median survival time was 3 months for patients who received a radiation dose of 55 Gy or less, 8.6 months for doses between 56 and 65 Gy, and 9.6 months for patients with a dose between 66 and 75 Gy (p < 0.01). In a multivariate analysis only the performance status maintained significance (p = 0.02) as a prognostic factor, while the dose range reached borderline significance (p = 0.09).No statistically significant survival prolongation was reached despite a dose escalation to 70 Gy.