The preliminary results of proton and carbon ion therapy for chordoma and chondrosarcoma of the skull base and cervical spine

PURPOSE: To evaluate the short-term outcomes in terms of tumor control and toxicity of patients with skull base or cervical spine chordoma and chondrosarcoma treated with intensity-modulated proton or carbon-ion radiation therapy. METHODS: Between 6/2014 and 7/2018, a total of 91 patients were treated in our Center. The median age was 38 (range, 4–70) years. Forty-six (50.5%) patients were treated definitively for their conditions as initial diagnosis, 45 (49.5%) patients had recurrent tumors including 14 had prior radiotherapy. The median gross tumor volume was 37.0 (range, 1.6–231.7) cc. Eight patients received proton therapy alone, 28 patients received combined proton and carbon ion therapy, 55 patients received carbon-ion therapy alone. RESULTS: With a median follow-up time of 28 (range, 8–59) months, the 2-year local control (LC), progression free (PFS) and overall survival (OS) rates was 86.2, 76.8, and 87.2%, respectively. Those rates for patients received definitive proton or carbon-ion therapy were 86.7, 82.8, and 93.8%, respectively. On multivariate analyses, tumor volume of > 60 cc was the only significant factor for predicting PFS (p = 0.045), while re-irradiation (p = 0.012) and tumor volume (> vs < 60 cc) (p = 0.005) were significant prognosticators for OS. Grade 1–2 late toxicities were observed in 11 patients, and one patient developed Grade 3 acute mucositis. CONCLUSIONS: Larger tumor volume and re-irradiation were related to inferior survival for this group of patients. Further follow-up is needed for long-term efficacy and safety.