Heavy ion (carbon ion) radiotherapy for skull base chordomas

Abstract

Skull base and paracervical chordomas are rare tumors originating from ectopic remnants of the embryonal notochord at the spheno- occipital synchondrosis. Although the first choice of treatment is surgical resection, complete resection is difficult due to the tumors’ close proximity to the critical organs. Thus, the residual tumor is treated with radiotherapy. Heavy ion (carbon ion) radiotherapy was initiated at the National Institute of Radiological Sciences in 1994. Carbon ions have a high relative biological effectiveness (RBE) and a favorable dose distribution compared with other ion species and photons. Therefore, carbon ion radiotherapy has shown promising results for radioresistant tumors. Between May 1995 and January 2012, a total of 50 patients with skull base or paracervical chordomas have been treated with carbon ion radiotherapy. This paper describes our efforts to estimate the outcome of carbon ion radiotherapy for patients with skull base and paracervical chordomas.