Feasibility of Proton Beam Therapy for Chordoma and Chondrosarcoma of the Skull Base

Abstract

We explored the general feasibility of proton beam therapy for chordoma and chondrosarcoma of the skull base. Clinical records and treatment-planning data of patients with the pathological diagnosis of chordoma or chondrosarcoma were examined. Proton beam therapy was administered for gross tumor mass as well as microscopic residual disease after surgery. The prescribed dose was determined to maximize the coverage of the target and to not exceed predefined constraints for the organs at risk. Eight cases of chordoma and eight cases of chondrosarcoma were enrolled. The median tumor volume was 40 cm 3 (range, 7 to 546 cm 3 ). The prescribed dose ranged from 50 to 70 Gy (relative biological effectiveness [RBE]), with a median of 63 Gy RBE. The median follow-up duration was 42 months (range 9 to 80 months). The overall survival rate was 100%, and the local control rate at 3 years of chordoma and chondrosarcoma were 100% and 86%. None of the patients developed radiation-induced optic neuropathy, brain stem injury, or other severe toxicity. Proton beam therapy is generally feasible for both chordoma and chondrosarcoma of the skull base, with excellent local control and survival rates.

Fifty-four-month survival in a 3-year-old child presenting with an aggressive metastatic dedifferentiated clival chordoma

“…Presurgical radiotherapy may be used to de-bulk disease 11 12. PBT often has a larger role in clival disease control, as high-dose radiation can be delivered precisely to the target area—with reduced damage to surrounding neurovascular tissue—compared to traditional photon radiation 7 9. Cutaneous seeding is a recognised complication of surgery, especially with poorly differentiated tumours 13…”

Historical development of the treatment of skull base tumours

“…26 In Japan, the results on 16 patients treated at Tsukuba were published with local control of 100% at 3 years for chordoma and 86% for chondrosarcoma and an overall survival rate of 100%. 27 At the Centre for Oncological Hadrontherapy (CNAO) in Italy, the preliminary results on the first patients treated with protons were recently reported with very low-toxicity rates (Fig. 2).…”

“…In the following years, a number of retrospective and prospective clinical trials were reported by institutions from the USA, Europe and Japan equipped with proton facilities showing that very favourable clinical results could be achieved with limited toxicity in the treatment of skull base tumours. [23][24][25][26][27] Most of the experiences focused on skull base chordoma and chondrosarcoma. At MGH, 375 chordomas and 246 chondrosarcomas of the base of skull were treated by protons obtaining 10-year local control rates of 54% and 98%, respectively.…”

Late toxicity of proton beam therapy for patients with the nasal cavity, para-nasal sinuses, or involving the skull base malignancy: importance of long-term follow-up

“…Although several reports [10][11][12] have shown that PBT holds promise for patients with skull base cancer, little is known about the frequency of late toxicity in clinical practice using PBT for these patients.…”