Diffusion tensor invasive phenotypes can predict progression-free survival in glioblastomas

Abstract

Introduction. Glioblastomas multiformes (GBM) remain incurable in most cases. Their invasion into normal brain makes current therapies ineffective. Post-mortem studies suggest about a 25% of GBMs invade less than 1 cm from the tumour bulk and 20% invade more than 3 cm. Aim of study. The study aims to use DTI to assess tumour extension and determine how previously reported patterns relate to the progression-free survival (PFS). Materials and methods. Twenty-five patients with GBM treated according to the EORTC/NCIC protocol were retrospectively analysed. Patients were imaged post-operatively at 1.5 T. The sequences were composed of standard anatomical and a standard DTI sequence. As described earlier p and q maps were constructed. For each of the p and q maps, regions of interest were drawn around the visible abnormality. Patients were assigned a diffuse, localised or minimally invasive pattern. Progression was defined according to the RANO criteria and PFS determined in days. Kaplan–Meier plots of survival for the three groups were plotted as were the proportion of patients who had not progressed at 24 months. Results. The median PFS for the diffuse group was 278 days, for the localised group 605 days and 820 days for the minimally invasive group. Three-fourth of the minimally invasive group were progression-free at 24 months (LOG RANK 9.25; p = 0.010). Conclusion. It is possible to identify three invasive phenotypes in GBMs using Diffusion tensor imaging , and these three phenotypes have different progression free survival. A minimal phenotype (20% of patients) predicts a greater delay to progression.