Carbon Ion Radiotherapy in a Hypofractionation Regimen for Stage I Non-Small Cell Lung Cancer

In 1994, we began using carbon-ion radiotherapy (CIRT) for the treatment of peripheral stage I nonsmall cell lung cancer (NSCLC). Between 1994 and 1999, a phase I/II dose escalation study of the treatment of stage I peripheral NSCLC was conducted to determine the optimal dose of therapy and evaluate whether progressing to hypofractionated CIRT was feasible. Another purpose of these trials was to develop precise and safe irradiation techniques with maximum sparing of normal tissue. Two phase I/II clinical trials demonstrated the optimal doses of 90.0 GyE in 18 fractions over six weeks (Protocol #9303) and 72.0 GyE in nine fractions over three weeks (Protocol #9701) for achieving more than 95% local control with minimal pulmonary toxicity.As a next step, we conducted two successive phase II trials. The first trial (Protocol #9802) used a regimen of 72 GyE per nine fractions over three weeks, and the second trial (Protocol #0001) used a regimen of four fractions over one week at a fixed dose of 52.8 GyE for stage IA patients and 60GyE for stage IB patients. In these phase II trials, the local control rate (LCR) for all patients was 91.5%, while that for patients with T1 and T2 tumors was 96.3% and 84.7%, respectively. The 5-year cause-specific survival rate (CSS) was 67.0% (IA: 84.4, IB: 43.7), and the overall survival (OS)rate was 45.3% (IA: 53.9, 1B: 34.2). No adverse events greater than grade 2 occurred in the lungs.In 2003, we initiated a phase I/II clinical trial (Protocol #0201) as a dose escalation study using a single fraction. The initial total dose was 28.0 GyE administered and escalated in increments of 2.0GyE each, up to 50.0 GyE. That clinical trial ended in February 2012 and remains in follow-up. In this article, we investigated the preliminary results of this phase I/II trial.The Cancer Symposium: Advanced Radiation Oncology Treatment Strategies with Photon, Proton, and Carbon Ion Radiatio