Purpose: The purpose of this work was to evaluate the results of high-dose radiation treatment using carbon ion therapy, alone or combined with intensity-modulated radiation treatment (IMRT), in patients with sacral chordoma.
Materials and methods: Between 2009 and 2012, 56 patients with sacral chordoma were treated in our center. The tumor was located above S3 in 33 patients and in S3 or below in 23 patients. In all, 41 patients received radiation therapy for the primary tumor, while 15 patients were treated for the recurrent tumor. Toxicity was measured using NCI CTCAE v.4.03. Local control (LC) and overall survival (OS) were evaluated with the Kaplan-Meier method.
Results: A total of 23 patients were irradiated with carbon ions in combination with photon IMRT, while 33 received carbon ion therapy only. Forty-three patients had a macroscopic tumor at treatment start with a median tumor size (GTV) of 244 ml (range 5-1188 ml). The median total dose was 66 Gy (range 60-74 Gy; RBE). After a median follow-up time of 25 months, the 2- and 3-year local control probability was 76 % and 53 %, respectively. The overall survival rate was 100 %. Treatment for primary tumor and male patients resulted in significant better local control. No higher toxicity occurred within the follow-up time.
Conclusion: High-dose photon/carbon ion beam radiation therapy is safe and, especially for primary sacral chordomas, highly effective. A randomized trial is required to evaluate the role of primary definitive hypofractionated particle therapy compared with surgery with or without adjuvant radiotherapy.