The higher sensitivity and specificity of amino-acids (L-[methyl-11C]-methionine, MET and O-(2-(1)-Fluoroethyl)-L-tyrosine, FET) positron emission tomography (AA-PET) in the diagnosis of gliomas in comparison to computed tomography (CT) and magnetic resonance imaging (MRI) was demonstrated in many studies and is the rationale for using them in target volume delineation of these tumors. Several clinical trials have demonstrated the significant differences between AA-PET and standard MRI in gross tumor volume (GTV) delineation for treatment planning.~A small prospective study in patients with recurrent high grade gliomas treated with stereotactic fractionated radiotherapy (SFRT) showed a significant improvement in survival when AA-PET or single photon emission tomography (AA-SPECT) were integrated in target volume delineation, in comparison to patients treated using CT/MRI alone (Grosu et al. 2005).~However, there are no randomized studies demonstrating the impact of AA-PET based irradiation treatment on the clinical follow-up in comparison to a traditional MRI/CT based treatment.~The goal of this study is to evaluate the impact of radiotherapy target volume delineation based on AA-PET (new strategy) on the clinical outcome of patients with recurrent glioblastoma (GBM) compared to target volume delineation based on contrast enhanced T1 weighted MRI (T1Gd-MRI) (traditional, established strategy). Concerning therapeutic safety, the topography of recurrence outside the primary target volume as well as the localization of necrosis after the re-irradiation will be determined. All side effects will be assessed by CTCAE version 4.0 and the safety analyses will present the worst grade of acute and late side effect by treatment arm for the whole study period (treatment and follow up). Patients will be asked to complete a quality of life (QoL) questionnaire (as assessed by the E-ORTC QLQ-C15 PAL) in regular time intervals.~This will be the first phase II randomized study evaluating the impact of molecular imaging on outcome after radiotherapy in brain tumor patients.~Another goal of the technical part of this study is the development of a standardized physical-technical methodology for the integration of AA-PET and other imaging biomarkers in tumor volume delineation in radiation therapy.
This study is designed to evaluate the impact of radiotherapy target volume delineation based on AA-PET compared to target volume delineation based on contrast enhanced T1 weighted MRI (T1Gd-MRI) on the clinical outcome of patients with recurrent glioblastoma (GBM) as well as concerning therapeutic safety of the respective strategy.