Carbon Ion Radiotherapy for Skull Base Chordoma

Objective: To present the results of the clinical study of carbon ion radiotherapy (CIRT) for skull base and paracervical spine tumors at the National Institute of Radiological Sciences in Chiba, Japan. Methods: The study is comprised of three protocols: a pilot study, a phase I/II dose escalation study, and a phase II study. All the patients were treated by 1.6 fractions for 4 weeks with total doses of 48.0, 52.8, 57.6, and 60.8 Gy equivalents (GyE). Results: As a result of the dose escalation study of CIRT for skull base tumors, a dose fractionation of 60.8 GyE/16 fractions for 4 weeks was decided as the recommended dose because of acceptable normal tissue reactions and good local tumor control. Conclusions: Preliminary results of the phase II clinical study of CIRT for skull base chordoma showed local control at 5 years at 100%, and normal tissues showed a mild reaction without any severe morbidity of important organs.