Uncertainties of RBE in treatment planning for ion beam tumor therapy: Experimental and modeling aspects

The increased relative biological effectiveness (RBE) of carbon ion beams represents one of the major ra- tionales for their application in radiotherapy. Due to the de- pendence of RBE e.g. on the dose level, penetration depth and the biological endpoint biophysical models are required in order to fully take into account these details in treatment planning. It is therefore of great interest to investigate the accuracy of the model predictions. For the assessment of this accuracy, the uncertainties of the experimental data represent the relevant measure. Therefore, we first propose generalized methods for the uncertainty analysis of larger sets of experimental data. The analysis of the model predictions is then focused on the investigation of sys- tematic deviations with respect to the experimental data. This includes a sensitivity analysis, where the model parameters are discussed with respect to their clinical relevance.