Radiation therapy is among the most common and effective therapies employed in both curative and palliative management of cancer patients. About 50% of all patients diagnosed with localized malignant tumors are treated with radiation, usually high-energy X-rays, as a part of the initial cancer therapy. Many years ago, it was proposed that high-energy ions might be successfully employed in the treatment of localized tumors, owing their physical and biological advantages toward X-rays. Indeed, high-energy charged particles are characterized by a more favorable tissue depth-dose distribution and higher relative biological effectiveness (RBE) compared with X-rays. Currently, many facilities in the U.S.A., Europe, and Japan use highenergy protons and carbon ions for the treatment of solid tumors and several new centers are under construction. These types of therapies present very high costs due to the expensive technologies used in building accelerators and for beam delivery. Therefore, the debate on cost: benefit ratio of these techniques is ongoing, although strong evidence suggests that charged particle therapy provides an important clinical advantage in treatment of localized tumors. In this chapter, we will describe clinical applications and results of charged particle radiotherapy compared to X-rays, and identify and discuss important questions that need to be addressed in this field.
Keywords: Radiation therapy, x-rays, -rays, high-energy photons, argon, carbon, Ion, biological effective dose (BED), relative biological effectiveness (RBE), ionizing radiation, radium, nuclear reactors, particle accelerators, cycle accelerators, linear accelerator, conformal radiotherapy, stereotactic radiotherapy, gamma knife, neutron beam therapy, proton beam therapy.