Moderately hypofractionated carbon ion radiotherapy for prostate cancer; A prospective observational study "gUNMA0702"

Background: Carbon ion Radiotherapy for prostate cancer is widely used, however reports are limited from single institute or short follow up. We performed a prospective observational study (GUNMA0702) to evaluate the feasibility and efficacy of carbon ion radiotherapy for localized and locally advanced prostate cancer. Methods: Between June 2010 and August 2013, 304 patients with localized prostate cancer were treated, with a median follow-up duration of 60 months. All patients received carbon ion radiotherapy with 57.6 Gy (RBE) in 16 fractions over 4 weeks. Hormonal therapy was given according to the risk group. Toxicity was reported according to the Common Toxicity Criteria for Adverse Event, Version 4.0 by the National Cancer Institute. Results: The overall 5-year biochemical relapse-free rate was 92.7%, with rates of 91.7, 93.4, and 92.0% in low-risk, intermediate-risk, and high-risk patients, respectively. The 5-year local control and overall survival rates were 98.4 and 96.6%, respectively. Acute grade 3 or greater toxicity was not observed. Late grade 2 and grade 3 genitourinary and gastrointestinal toxicity rates were 9 and 0.3%, and 0.3, and 0%, respectively. Conclusions: The present protocol of carbon ion radiotherapy for prostate cancer provided low genitourinary and gastrointestinal toxicity with good biochemical control within 5 years. Trial registration: University Medical Information Network Clinical Trial Registry number: UMIN000003827.