Up-to-date Results of Carbon-ion Radiotherapy for Prostate Cancer: Analysis of 1,144 Patients

Background: The carbon ion radiotherapy (C-ion RT) for the prostate cancer was started in 1995 using the Heavy-Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS), Japan. After preceding phase I/II dose escalation studies of 20 fractions over 5 weeks, a phase II study was initiated in April 2000 using the treatment techniques and the recommended dose fractionation established by the phase I/II studies. This study was also successfully completed in October 2003 when the C-ion RT for the solid tumors including the prostate cancer was approved as ,Advanced Medicine, from the Ministry of Health, Labor, and Welfare. Materials and methods: A phase II study of C-ion RT (9904[1]-[3]) for localized prostate cancer (T1b-T3bN0M0) was started from April 2000. A C-ion RT schedule of 66.0GyE/20fr./5weeks, 63.0GyE/20fr./5w and 57.6GyE/16fr./4w were used in 9904[1], 9904[2] and 9904[3] trials, respectively. The patients with low-risk prostate cancer were treated with C-ion RT alone, and the patients with intermediate-risk and high-risk prostate cancer were treated with C-ion RT combined with hormonal therapy of 6 months and >24 months, respectively. Biochemical failure was defined as PSA increase of 2.0ng/ml above nadir after the treatment.Results: A total of 1,144 patients were enrolled to the clinical study. Out of 1,144 patients, more than 50% patients were categorized as high-risk group with T3 clinical stage, Gleason,s score of 8 or higher, or PSA of 20 or higher. The 5-year overall survival rate and biochemical relapse free rate of the entire group was 95.7% and 91.0%, respectively. Biochemical relapse free rates of low-, intermediate- and high-risk patients were 90.1%, 94.2% and 89.7%, respectively. T-stage, Gleason score was significant prognostic factors for both the biochemical control and patient survival and initial PSA was also a predictive factor for survival. Regarding the late radiation toxicity, incidence of rectal toxicity of grade 2 or worse was 1.1% and that of genitourinary toxicity was 6.5%, respectively. In addition, incidence of the toxicity in the patients treated with more hypofractionated C-ion RT of 16 fractions over 4 weeks were lower than those of 20 fraction-treatment. Conclusions: These favorable outcomes can be thought as apparent evidence of physical and biological advantages of the hypofractionated C-ion RT.The 17th ECCO- 38th ESMO- 32nd ESTRO European Cancer Congres