ABSTRACT
Protons indisputably have a superior physical dose distribution compared to classically used photons, since they lose most of their energy in a small region called the Bragg peak that can be positioned in the target volume. Optimal use of proton therapy requires the selection of patient populations for which use of protons may offer advantages, comparison with alternative treatment techniques, and individualized optimization of the selected technique. Different types and stages of tumor are treated using different treatment modalities such as fractionated photon therapy using a linear accelerator, single fraction stereotactic radiotherapy, proton therapy, or brachytherapy using implanted radiation sources, all with the aim to maximize the probability of curing the patient while limiting toxicity to normal tissues. Each treatment modality possesses many parameters that can be used to optimize its application. In the presence of oxygen, photon irradiation leads to the formation of reactive oxygen species.
