Signal Transduction and Heavy Ion Radiation Therapy: Biological Mechanisms, Biological Quality Assurance, and New Multimodality Approach

High linear energy transfer (LET) radiotherapy has an excellent dose distribution and relative biological effectiveness (RBE). As the RBE of particle beams for therapy is important in terms of determining the dose prescription, we have to evaluate an accurate and reliable assessment method. Recently, several particle therapy facilities will open; however, the dose estimation is still not uniform. We have to confirm the quality assurance procedures among several facilities. Excellent local effect has been already achieved by treatment of monotherapy of carbon ion radiotherapy. The efficacy of carbon ion radiotherapy has been confirmed by taking advantage of the physical and biological properties. In addition, we have to gain the higher survival rate for locally advanced tumor with potentially metastasis. This paper reviews briefly background of carbon ion radiotherapy, biophysical characters, biological characters, and several radiobiological factors. The potential benefit of multimodality treatment will be also discussed to further improve therapeutic outcomes.