Skull Base and Upper Cervical Spine Tumors

Abstract

Major types of skull base and upper cervical spine tumors include chordoma, chondrosarcoma, and olfactory neuroblastoma, for which complete resection is rarely achieved because of the vicinity to the critical organ structure. Radiotherapy is the second treatment option; however, the limiting factor for photon radiotherapy conventionally applied to skull base and upper cervical spine tumors is damage to adjacent normal tissues, owing to poor local control. On the other hand, proton radiotherapy with its superior physical spatial distribution has provided a major improvement in local control in view of possible dose escalations. However, in certain patient groups, local control with proton radiotherapy is difficult to achieve even at elevated doses. For example, the reported 5-year local control rates for skull base chordoma after proton therapy ranged from 46 to 81 %. Therefore, the high linear energy transfer of carbon ion radiotherapy (C-ion RT) has a promising potential for the treatment of skull base tumors, especially chordoma. The 5-year local control and overall survival rates for 44 chordoma patients treated with carbon ion radiotherapy were 88 and 87 %, respectively. The 5-year actuarial local control and overall survival rates for 12 chondrosarcoma patients were 86 and 63 %, respectively. Acute and late normal tissue reactions were within acceptable limit. Thus, C-ion RT can be a promising treatment option for skull base and upper cervical spine tumors.