Spinal
chordomas cannot be treated with an effective dose using conventional
radiation therapy (RT) without exceeding the tolerance dose of the spinal cord while ensuring sufficient target coverage at the same time. In this study we investigate the potential physical advantages of combined photon intensity-modulated
radiation therapy (IMRT) and raster-scanned
carbon ion RT over photon IMRT alone. For a representative patient we generated a
carbon ion RT plan and a photon IMRT plan. Additionally, combined plans consisting of both
carbon ions and photon IMRT were calculated using ratios of 20:40 GyE, 30:30 GyE and 40:20 GyE. The best target coverage was obtained using
carbon ions alone. Using a combination of photon IMRT and
carbon ions, the target coverage was better than with photon IMRT alone. Due to the applied dose constraints, the sparing of the spinal cord was comparable for all plans. Using
carbon ions alone, the non-target tissue volume irradiated to at least 30 GyE/50.4 GyE was reduced by 72%/84% compared to photon IMRT alone. These advantages were evident even with combined techniques. The actually delivered dose distribution is expected to be more dependent on patient misalignment with
carbon ions compared with photon IMRT. A combination of
carbon ions and photon IMRT might be preferable in order to profit by the physical advantages of
carbon ions while ensuring a safe treatment.