Biological Treatment Planning for Tumor Therapy with Carbon Ions

Treatment planning for carbon ion therapy requires careful consideration and quantification of the biological effect of heavy ions. Since the radiation damage invoked by swift heavy particles considerably differs from that of photons, the relative biological effectiveness (RBE) must be taken into account to determine the relevant biologically equivalent dose. The RBE depends on many different parameters, such as the dose level, the ion species and energy as well as the biological endpoint. Currently, the Local Effect Model (LEM) developed at GSI is the only model that is used for treatment planning which takes these dependences into account. Here, we introduce the main ideas of the LEM and present its recent developments, which result in a better model accuracy when compared to experimental data. Further, we present the implementation of the LEM into the treatment planning software and discuss the potential advantages of carbon ions compared to conventional and proton irradiation.