Five-Year Clinical Outcomes Of 51.6Gy (RBE) In 12-Fractionated Carbon-Ion Radiotherapy For Localized Prostate Cancer: Two Prospective Analyses

Abstract

Although 51.6 Gy (relative biological effect [RBE]) in 12-fractionated over a 3-weeks carbon-ion radiotherapy (CIRT) has been performed from 2010 and is now regarded as standard CIRT treatment, there is no report of clinical outcomes with long term follow-up after CIRT using the dose prescription. The purpose of this study was to reveal the clinical outcome after CIRT of the dose prescription with median follow up duration more than 5 years at our institution. A total of 257 patients with localized prostate cancer who received CIRT of 51.6 Gy (RBE) in 12 fractions in two protocols (9904-4 and 1002) between July 2010 and February 2014 were analyzed. Biochemical relapse free survival (bRFS) defined by the Phoenix definition and the survival rates were calculated. The incidence of acute and late adverse events was evaluated based on the Common Terminology Criteria for Adverse Events ver. 4.0. The numbers of low-, intermediate-, and high-risk group patients was 41(15.9%), 112(43.6%), and 104(40.5%), respectively. The median follow-up period of the surviving patients was 6.0years (range, 1.1-9.5years). The 5-year bRFS rates of the low-, intermediate, high-risk groups were 94.7%,92.1%, and 92.5%, respectively. The disease specific survival of the entire group was 100%. The acute and late gastrointestinal (GI) G2 toxicities were 0 and 2 (0.8%), respectively. The acute and late genitourinary (GU) G2 toxicities were 16 (6.2%) and 3 (1.2%), respectively, including the acute and late G2 hematuria of 1 (0.4%) and 1 (0.4%), respectively. None ≥G3 toxicities were observed. The 12-fractionated CIRT of 51.6Gy (RBE) for localized prostate cancer was good therapeutic and showed low toxicity.