Particle therapy in the future of precision therapy

Abstract

The first hospital-based treatment facilities for particle therapy started operation about thirty years ago. Since then, the clinical experience with protons and carbon ions has grown continuously and more than 200,000 patients have been treated to date. The promising clinical results led to a rapidly increasing number of treatment facilities and many new facilities are planned or under construction all over the world. An inverted depth-dose profile combined with potential radiobiological advantages make charged particles a precious tool for the treatment of tumours that are particularly radioresistant or located nearby sensitive structures. A rising number of trials have already confirmed the benefits of particle therapy in selected clinical situations and further improvements in beam delivery, image guidance and treatment planning are expected. This review summarises some physical and biological characteristics of accelerated charged particles and gives some examples of their clinical application. Furthermore, challenges and future perspectives of particle therapy will be discussed.

Figure 1.

Plan of the HIT Center in Germany. This hospital-based facility can treat patients with protons and heavy ions. Particles are accelerated in a synchrotron (at the back left) and three rooms are available for patient treatment (red arrows). The third treatment room on the right features a heavy ion gantry, enabling flexible positioning of the beam delivery system. HIT, Heidelberg Ion Beam Therapy.

Figure 2.

Schematic diagram of depth–dose distributions of different radiation modalities.

Figure 3.

Exemplary treatment plan comparison in a young patient with craniopharyngioma. A: 3D-CRT with photons, B: IMRT (VMAT) with photons, C: PRT with two opposing beams. Highlighted OAR: Brain stem. IMRT, intensity modulated radiation therapy; OAR, organ at risk; PRT, proton beam radiotherapy; VMAT, volumetric modulated arc therapy