Purpose: Analysis of the results of hypofractionated conformal carbon ion radiotherapy for localized prostate cancer was performed, with special regard to normal tissue morbidity and biochemical relapse-free rate (bNED).
Methods and materials: Analysis was performed for 201 patients treated with the dose fractionation regimen established during three clinical trials performed between June 1995 and February 2004. Outcomes were measured in terms of toxicity, survival, freedom from local recurrence, and bNED.
Results: No Grade 3 or higher toxicities were observed in either the rectum or genitourinary system, and the incidences of Grade 2 rectum or genitourinary morbidity were only 1.0% and 6.0%, respectively. The overall 5-year biochemical relapse-free survival was 83.2% without any local recurrence. Gleason score, initial PSA, and T stage were all significant prognostic factors for bNED, which was 97.1% in patients with Gleason score < or =7 and initial PSA <20 ng/mL.
Conclusion: Hypofractionated carbon ion radiotherapy with the established dose fractionation regimen yielded satisfactory bNED without local recurrence and with minimal morbidity. Long-term results are necessary to confirm the utility of carbon ion radiotherapy in the treatment of localized prostate cancer.