PSI/Center for Proton Therapy, Villigen
As 3D-conformal treatment has become the clearly accepted goal of radiation oncology, charged particle treatment with protons and heavier ions ascended to the forefront. After three decades of > 50,000 treated patients, proton radiotherapy has established itself as an accepted and often preferred treatment modality for tumors requiring high-dose conformal irradiation. It has continuously demonstrated its ability of dose reduction to normal tissues, thus becoming the RT modality of choice for pediatric malignancies. Simultaneously, heavier ions, notably carbon ion therapy, have been developed at fewer centers, involving approximately 5,000 patients worldwide. The rational is primarily based on a comparable dose distribution compared to protons but with the potential benefit of increased biologic effectiveness. Radioresistant tumors are believed to benefit most from carbon ion therapy. The current status of clinical results will be discussed. The majority of clinical data have been obtained on rare, but difficult to treat tumors, for example mesenchymal tumors of the skull base and paraspinal region. Here, an approximate 10-15% tumor control advantage has been observed for particle therapy. Most clinical data are based on Phase I/II protocols. The anticipated future direction of the role of particle therapy in medicine is a complex subject and involves an interplay of radio-biology, accelerator physics and radiation oncology.
