[Clinical evaluation and perspective of charged particle therapy]

In cancer radiotherapy, protons and heavy-ions share the same beneficial property of superior dose localization. In addition, heavy-ions are high-LET radiations and have increased biological effectiveness when compared with photons or protons. The potential indications for them are those diseases which are usually hard to cure with conventional radiations. At present there are 17 operating facilities world-wide for proton therapy, which in Japan is being conducted at the National Institute of Radiological Sciences (NIRS) and Tsukuba University (PMRC). Currently, Massachusetts General Hospital (MGH) in USA and the National Cancer Institute East Hospital in Japan are building a hospital-based proton facility, both of them will have a fixed energy cyclotron (230MeV). New plans for commencing proton therapy are also proposed by many other institutions in the world. As with heavy-ion therapy, clinical trials have been carried out since 1994 using carbon-ions generated by HIMAC (Heavy-ion medical accelerator in Chiba) at NIRS. The HIMAC is the world's only heavy-ion accelerator complex dedicated to medical use in a hospital environment. The Hyogo prefecture has just decided to build a similar ion therapy facility. As of February 1997, a total of 230 patients were treated in carbon-ion Phase I/II studies at NIRS. So far, carbon-ions appear to be effective in such cases as locally advanced tumors and non-squamous tumors.