Carbon-ion radiotherapy—basic and clinical studies

Radiotherapy using charged and/or high-LET particles has a long history, starting with proton beams. In vitro data clarify that RBE (Relative Biological Effectiveness) increases with LET up to approximately 150 keV/μm for carbon-12 and neon-20 ions. In vivo studies show that tumor control probabilities after single doses of gamma rays shift to higher doses when tumors were irradiated with 5-fractionated doses, while such a shift is not observed for carbon ions, and that tumor reoxygenation is accelerated after carbon ions compared to γ-rays. The RBE for tumor control is greater than that for the skin response when fibrosarcoma and skin of mice are irradiated with 3-5 dose fractions of 290 MeV/u carbon ions. Experimental results of secondary tumors induced by carbon ions are included. Clinical results for various malignancies are also presented here.