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.