Adaptive Radiotherapy for Glioblastoma Multiforme - The Impact on Disease Outcome.

Abstract

To study the changes of glioblastoma multiforme during chemoradiotherapy (CRT) and to evaluate the impact of changes on dosimetry and clinical outcomes. Forty-three patients underwent volumetric imaging-based replanning. Prognostic factors and gross tumor volume changes in relation to overall survival and the effect of adaptive replanning were statistically analyzed. Patients with total tumor removal, with shorter time to CRT (<27 days), with methylated O-6 methylguanine DNA methyltransferase and good performance status (>60%) had better survival. Tumor shrinkage in 24 patients resulted in improved survival compared to 19 in whom tumor was unchanged or progressed (25.3 vs. 11.1 months, p=0.04). Adapted planning target volume allowed a reduction in irradiated volume, while increasing survival (12.06 vs. 28.98 months, p=0.026). Tumor response during CRT has significant impact on the outcome. Adaptation of the planning target volume to the tumor changes proved to be beneficial and warrants further investigation.