Carbon ion radiotherapy holds great promise for
cancer therapy. Clinical data show that
carbon ion radiotherapy is an effective treatment for
tumors that are resistant to X-ray
radiotherapy. Since 1994 in Japan, the National Institute of Radiological Sciences has been heading the development of
carbon ion radiotherapy using the Heavy Ion Medical Accelerator in Chiba. The Gunma University Heavy Ion Medical Center (GHMC) was established in the year 2006 as a proof-of-principle institute for
carbon ion radiotherapy with a view to facilitating the worldwide spread of compact accelerator systems. Along with the management of more than 1900
cancer patients to date, GHMC engages in translational research to improve the treatment efficacy of
carbon ion radiotherapy. Research aimed at guiding patient selection is of utmost importance for making the most of
carbon ion radiotherapy, which is an extremely limited medical resource. Intratumoral
oxygen levels, radiation-induced cellular apoptosis, the capacity to repair
DNA double-strand breaks, and the mutational status of
tumor protein p53 and epidermal growth factor receptor genes are all associated with X-ray sensitivity. Assays for these factors are useful in the identification of X-ray-resistant
tumors for which
carbon ion radiotherapy would be beneficial. Research aimed at optimizing treatments based on
carbon ion radiotherapy is also important. This includes assessment of dose fractionation, normal tissue toxicity,
tumor cell motility, and bystander effects. Furthermore, the efficacy of
carbon ion radiotherapy will likely be enhanced by research into combined treatment with other modalities such as
chemotherapy. Several clinically available chemotherapeutic drugs (
carboplatin,
paclitaxel, and
etoposide) and drugs at the developmental stage (Wee-1 and
heat shock protein 90 inhibitors) show a sensitizing effect on
tumor cells treated with
carbon ions. Additionally, the efficacy of
carbon ion radiotherapy can be improved by combining it with
cancer immunotherapy. Clinical validation of preclinical findings is necessary to further improve the treatment efficacy of
carbon ion radiotherapy.