Heavy-ion therapy is the use of particles more massive than protons or neutrons, such as carbon ions. Compared to protons, carbon ions have an advantage: due to the higher density of ionization at the end of their range, correlated damages of the DNA structure within one cell occur more often so that it becomes more difficult for the cancerous cell to repair the damage. This increases the biological efficiency of the dose by a factor between 1.5 and 3. Compared to protons, carbon ions have the disadvantage that beyond the Bragg peak, the dose does not decrease to zero, since nuclear reactions between the carbon ions and the atoms of the tissue lead to production of lighter ions which have a higher range. Therefore, some damage occurs also beyond the Bragg peak.
By the end of 2008, more than 5,000 patients had been treated using carbon ions.
At the end of 2013, around 13 000 patients had received carbon-ion therapy
Particle beams offer benefits over conventional photon radiation for the treatment of many tumors. Currently, 49 facilities worldwide— including 14 in the US—are producing proton beams, and another 29 are under construction. But carbon-ion therapy, which can benefit patients with deepseated or radiation-resistant tumors, remains in relative infancy, with eight centers operating and four under construction as of 1 April.
Carbon-ion treatment centers in operation
The Particle Therapy Co-Operative Group lists treatment centers in operation or in the planning or construction stage. At least five centers using carbon ions are in operation, four in Japan: the HIMAC at Chiba, the HIBMC at Hyogo, and Gunma University's Heavy Ion Medical Center in Maebashi, and SAGA-HIMAT, Tosu. A fifth in Japan is currently under construction, tentatively named "i-ROCK". In Germany, treatment at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt, which is primarily a physics laboratory, has been discontinued in 2008, but the new HIT in Heidelberg, which is a dedicated facility, started in November 2009. The HIT facility is using robotic technology with sub millimeter precision to position the patients. Moreover, Heidelberg has developed and took into clinical operation in 2011 the first gantry worldwide for proton and ion beams. The rotating part of this structure has a weight of 600 tons. The CNAO in Pavia, Italy opened in 2011 and will be one of the most advanced centers[clarification needed] for particle therapy with hadrons. CNAO will combine precise dose delivery with highly accurate patient alignment based on stereoscopic X-ray imaging. Sophisticated approaches in image-guided particle therapy (IGPT) augments the radiotherapy machines with imaging capabilities and the latest computer vision technology to increase accuracy of target localization and enable patient alignment accuracies of 0.5 mm and better. In January 2015 the Shanghai Proton and Heavy Ion Centre opened after successfully completing the clinical trials. The Marburg ion treatment facility, MIT (Marburger Ionenstrahl Therapie) treated their first patient in October 2015.