On PTV definition for glioblastoma based on fiber tracking of diffusion tensor imaging data.

Barbara Witulla,Arnd Dörfler,Rainer Fietkau,Nicole Goerig,Christoph Bert,Tobias Engelhorn,Benjamin Frey,Michael Uder,Frederik Bernd Laun,Florian Putz,Jonathan H Sherman

doi:10.1371/journal.pone.0227146

Abstract

Radiotherapy (RT) is commonly applied for the treatment of glioblastoma multiforme (GBM). Following the planning target volume (PTV) definition procedure standardized in guidelines, a 20% risk of missing non-local recurrences is present. Purpose of this study was to evaluate whether diffusion tensor imaging (DTI)-based fiber tracking may be beneficial for PTV definition taking into account the prediction of distant recurrences. 56 GBM patients were examined with magnetic resonance imaging (MRI) including DTI performed before RT after resection of the primary tumor. Follow-up MRIs were acquired in three month intervals. For the seven patients with a distant recurrence, fiber tracking was performed with three algorithms and it was evaluated whether connections existed from the primary tumor region to the distant recurrence. It depended strongly on the used tracking algorithm and the used tracking parameters whether a connection was observed. Most of the connections were weak and thus not usable for PTV definition. Only in one of the seven patients with a recurring tumor, a clear connection was present. It seems unlikely that DTI-based fiber tracking can be beneficial for predicting distant recurrences in the planning of PTVs for glioblastoma multiforme.

Highlights

A good outcome in radiation therapy requires a good definition of the planning target volume by means of imaging techniques like computer tomography (CT) or magnetic resonance imaging (MRI)
A connection is present for seed b; i.e. it matters whether the tractography is started in the gross tumor volume (GTV) or in the recurrence volume
The results indicate that the usefulness of fiber tracking methods for inclusion of distant recurrences in the definition of the planning target volume (PTV) is rather limited for glioblastoma multiforme (GBM) patients

Summary

Introduction

A good outcome in radiation therapy requires a good definition of the planning target volume by means of imaging techniques like computer tomography (CT) or magnetic resonance imaging (MRI). In case of glioblastoma (GBM, annual incidence of approximately 5000 cases in Germany, which has a population of roughly 83 million people [2]), MRI images are acquired before and after surgical removal of the visible tumor area for defining the clinical target volume (CTV). The “American Society of Clinical Oncology” recommends resection with consequent external beam radiation therapy (RT) [3, 4]. The target volume should include the area of the tumor before resection and the cavity after resection. Should be taken into account when defining the target volume [3, 4].

Objectives

Methods

Results

Discussion

Conclusion