Advanced MRI for assessment of toxicity after photon and proton based radiation therapy in primary brain tumors.

In brain tumors, proton beam radiotherapy (RTx) reduces the radiation dose to healthy brain tissue outside the planning target volume compared to conventional photon based RTx. However, there is still a lack of prospective studies investigating the objective (i.e., surrogate imaging marker) and subjective (i.e., patient questionnaires) effects of photon vs. proton beam RTx for brain tumor patients. In this prospective study, primary brain tumor patients undergoing either photon- or proton-beam (chemo)RTx are being scanned using an advanced MRI protocol at 3T before RTx and at 3-monthly intervals thereafter. The MR protocol comprises conventional anatomical imaging (FLAIR, T1w, T2w, DWI) and state of the art MR sequences including quantitative T1, T2, T2* and Proton Density (PD) imaging (Figure 1), Diffusion Tensor Imaging, 2D MR spectroscopic imaging as well as ASL, T1* and T2* perfusion imaging.

In this NCT granted project, we will investigate qualitative and quantitative MR changes after photon and proton RTx in tumor tissue and surrounding normal appearing brain and correlate the results to the radiation dose fields as well as neurocognitive function and quality of life of the patients. The primary goal is to establish a rational for proton beam therapy in primary brain tumor patients with a long life expectancy and thus at risk of developing radiation sequelae (e.g., neurocognitive impairment, acute and late toxicity after RTx). Secondary goal is the combined analysis of the advanced multimodal MR data to identify infiltrative tumor tissue not visible on conventional MRI and predict local tumor control.