Charged particle beams to cure cancer: Strengths and challenges.

Charged particle therapy is the most advanced radiotherapy method in oncology. The favorable depth-dose distribution and the biological properties of charged particles have potentially a great benefit for reducing toxicity and increasing the local control. While the number of proton centers is exponentially growing worldwide, the therapy remains controversial due to the high cost and lack of level-I evidence of superior effectiveness compared to conventional X-rays. Here we will discuss the advantages and the challenges in both physics and biology to fully exploit the potential of ion therapy in medicine. The challenges include reducing the footprint and costs of accelerators, reducing range uncertainty, exploitation of the biological advantages such as the high effectiveness against hypoxic tumors, and to select patients with biology-driven personalized approaches. International collaboration in the field is likely to bring definite answers to these ongoing problems.