Current Status of Carbon Ion Radiotherapy in Japan

As compared to photon beams, carbon ion beams offer improved dose distributions in cancer radiotherapy,thus enabling dose concentration within a target volume while minimizing the dose in the surrounding normaltissues. Furthermore, carbon ions being heavier than protons provide a higher biological effectiveness, whichincreases with depth, reaching the maximum at the end of the beam\u27s range. This is an ideal property from thestandpoint of cancer radiotherapy. At the National Institute of Radiological Sciences (NIRS), the pioneer clinicalstudy on carbon ion radiotherapy (C-ion RT) was started in 1994 using carbon ions generated by Heavy IonMedical Accelerator in Chiba (HIMAC). So far, more than 6,000 patients have been treated, where the benefit ofC-ion RT over other modalities has been demonstrated for various tumor sites in terms of high local control andsurvival rates, as well as significant reduction in overall treatment time with acceptable toxicities in most cases.Efficacy of C-ion RT has been also demonstratred in other facilities in the world