History of charged particle radiotherapy

Abstract

Among various types of charged particles, protons and carbon ions have been most extensively used for cancer therapy around the world. In 1954, clinical application of proton beams was started for the first time in the world at Lawrence Berkeley National Laboratory (LBNL), which was shortly followed by Uppsala, Boston, Russia (three facilities), and Chiba. It is only after 1973, when computerized tomography (CT) was invented, that accurate calculation of dose distributions became feasible in clinical practice. In 1990, the world’s first hospital-based proton facility with a rotating gantry was built in Loma Linda. Since then, proton therapy has been applied to cancer treatment in an increasing number of facilities. Currently, there are about 36 facilities for proton beam therapy in operation, with still more facilities under construction or being planned in the world. As for the clinical application of heavier ions, the first patient was treated with helium ions in 1957 and with neon ions in 1975 at LBNL. Until it was closed in 1992, 2,054 patients were treated with helium ions and 433 patients with neon ions and other heavy ions. In 1994, the National Institute of Radiological Sciences (NIRS) in Japan started clinical application of carbon ions generated by Heavy Ion Medical Accelerator (HIMAC) in Chiba, which was the world’s first medically dedicated facility. Among various types of ion species, carbon ions were chosen for therapy because the biologically expressed dose distribution was assumed to be superior to other ions and the amount of high-LET components would be sufficient to ensure biological benefit in controlling photon-resistant tumors. By March 2013, more than 7,300 patients were treated at NIRS. In 1997, carbon-ion therapy was also initiated at Gesellschaft für Schwerionenforschung (GSI) in Germany to treat 440 patients until 2005, when it was closed and succeeded by Heidelberg University. Currently, there are six carbon therapy facilities in operation and several other facilities under construction in the world.