Carbon Ion Radiotherapy for Skull Base and Paracervical Chordomas

Purpose/Objective(s): To estimate the toxicity and efficacy of carbon ion radiotherapy for skull base and paracervical chordomas.Material/Methods: Between April 1997 and August 2008, a total of 54 patients with skull base or paracervical tumors were treated with carbon ion radiotherapy for phase I/II or phase II clinical trials. The phase I/II dose escalation trial was performed up to the fourth-stage dose level (48 GyE, 52.8 GyE, 57.6 GyE and 60.8 GyE). A total carbon ion dose was delivered in 16 fractions over four weeks. From April 2004, a phase II clinical trial was initiated under the Highly Advanced Medical Technology scheme with an irradiation schedule of 60.8 GyE in 16 fractions over four weeks. Thirty-one patients with chordoma were enrolled in these studies and analyzed.Results: The 31 patients consisted of 14 males and 17 females. The age range was from 16 to 76, with a median of 47 years. Median follow-up time was 52 months (range, 9-127 months). At the time of analysis, there was no evidence of any serious acute or late reactions. A late grade 2 brain reaction was detected in 1 patient irradiated with 60.8 GyE, but no other adverse reactions were discovered. The tumor effect remains mostly as stable disease within the six months of carbon ion radiotherapy, and the tumor size showed no dramatic change in most of the cases for a long time. Local control (LC) was defined as showing no evidence of tumor regrowth by MRI, CT, physical examination, or biopsy. In 31 chordoma patients, the five-year LC and overall survival (OS) rates were 78% and 85%, respectively. These patients were divided into two groups; a low-dose group (n=10) irradiated with doses ranging from 48 to 57.8 GyE and a high-dose group (n=21) irradiated with 60.8 GyE. The five-year LC rates were 60% for the low-dose group and 93% for the high-dose group. The five-year OS rates were 90% for the low-dose group and 84% for the high-dose group. Although one patient from the high dose group died due to intercurrent hepatic failure, the cause-specific survival rate was 89% for the high-dose group.Conclusion: The carbon ion dose of 60.8 GyE improves local control. Additionally, we did not observe severe toxicity to critical organs such as the brainstem, spinal cord and optic nerves.The 51st ASTRO Annual Meetin