The Current Status and Future Directions of Heavy Charged Particle Therapy in Medicine
Abstract
As aggressive, 3D-conformal treatment has become the clearly accepted goal of radiation oncology, heavy charged-particle treatment with protons and heavier ions has concurrently and relentlessly ascended to the forefront. Protons and helium nuclei, with relatively low linear-energy-transfer (LET) properties, have consistently been demonstrated to be beneficial for aggressive (high-dose) local treatment of many types of tumors. Protons have been applied to the majority of solid tumors, and have reached a high degree of general acceptance in radiation oncology after three decades and 55,000 patients treated. However, some 15% to 20% of tumor types have proven resistant to even the most aggressive low-LET irradiation. For these radio-resistant tumors, treatment with heavier ions (e.g., carbon) offers great potential benefit. These high-LET particles have increased relative biological effectiveness (RBE) that reaches its maximum in the Bragg peak. Irradiation with these heavier ions offers the unique combination of excellent 3D-dose distribution and increased RBE. We are presently witnessing several, important parallel developments in particle therapy. Protons will likely continue their exponential growth phase, and more compact design systems will make protons available to a larger patient population—thus becoming the "heavy charged particle of choice" for Cancer Centers with limited financial resources. In parallel, major academic efforts will further advance the field of heavier ion therapy, exploring all opportunities for particle treatment and continuing the search for the ideal particle(s) for specific tumors. The future of ion therapy will be best realized by clinical trials that have ready access to top-quality delivery of both protons and heavier ions that can be accurately shaped for treatment of a specific pathology, and which will permit direct randomized-trial comparison of the effectiveness of the various ions for different diseases. Optimal results will require: (1) sophisticated target delineation that integrates CT, MRI and PET imaging; (2) reliable RBE modeling algorithms; (3) efficient beam-scanning technology that compensates for organ movements; (4) online beam control proximal to and within the patient; and (5) better understanding of dose-fractionation parameters. The current status and the anticipated future directions of the role of particle therapy in medicine is a complex subject that involves a very intimate interplay of radiobiology, accelerator physics and radiation oncology. The intention of this relatively brief manuscript is to describe the underlying principles, present the historical developments, highlight the clinical results, focus on the technical advances, and suggest likely future directions. We have also attempted to present a balanced, consensus view of the past achievements and current strategies in particle therapy, in a manner of interest both to long-term experts and to educated newcomers to this field.
- Publication:
-
Application of Accelerators in Research and Industry: Twentieth International Conference
- Pub Date:
- March 2009
- DOI:
- 10.1063/1.3120064
- Bibcode:
- 2009AIPC.1099..410L
- Keywords:
-
- 87.53.-j;
- 68.37.Hk;
- 87.61.-c;
- Ionizing-radiation therapy physics;
- Scanning electron microscopy;
- Magnetic resonance imaging