Carbon Ion Radiotherapy for Prostate Cancer

Purpose: Analysis on the results of hypofractionated conformal carbon ion radiotherapy (C-ion RT) for localized prostate cancer was performed, with regard to normal tissue morbidity, biochemical relapse-free rate (bNED), and patient survival. Methods and Materials: Seven hundreds and forty prostate cancer patients who received C-ion RT established through two preceding dose-escalation studies were analyzed in regard to toxicity, survival, and bNED. Results: Concerning radiation morbidity, no grade 3 or higher toxicities were observed either in the rectum or genitourinary system (GU), and incidences of grade 2 rectum and GU morbidity were only 1.9% and 4.8%, respectively. Incidence of late GU toxicity in the patients treated with C-ion RT of 16 fractions was lower than that of 20 fractions. Overall bNED at 5 years was 90.2%, with only four local recurrences. The bNED of the C-ion RT of 16 fractions was comparable to that of 20 fractions. Gleason\u27s score, T-stage, and initial PSA were significant prognostic factors for bNED, and T-stage and initial PSA were also significant prognostic factors for overall survival rate. The duration of hormonal therapy also had an impact on biochemical control in high-risk patients, but it appeared possible to apply C-ion RT with short-course hormonal therapy to intermediate-risk patients. Conclusion: C-ion RT with the established dose fractionation regimen yielded satisfactory bNED with very few local recurrences, and with minimal morbidity. C-ion RT of 16 fractions could offer even lower incidence of GU toxicity than that of 20 fractions