Clinical Rationale and Indications for Particle Therapy.

Particle therapy is characterized by distinct physical properties leading to a reduction of integral dose compared to photons. While protons have an almost comparable biological effect, carbon ions and other heavier charged particles offer an increased relative biological effectiveness. The potential clinical benefit has been pointed out by several groups. Most likely, for protons, children have the largest margin of benefit since their normal tissue is very sensitive to radiation, and curative treatments lead to extremely long-term survivors having a lot of scope for long-term side effects. Many clinical studies, mostly of a retrospective nature, have shown promising results for various tumor types being treated with proton and heavy ion radiotherapy. Further clinical trials are needed in order to evaluate the opportunities of ion beam therapy and its prognostic influence on the general outcome, and many studies are currently recruiting patients. The aim here is to summarize current knowledge, possible clinical rationales, and indications for ion beam therapy.