A Japanese Multi-Institutional Phase II Study of Moderate Hypofractionated Intensity-Modulated Radiotherapy with Image-Guided Technique for Prostate Cancer

Abstract

Abstract Background Although moderate hypofractionated radiotherapy were one of standard regimens for localized prostate cancer, the efficacy of moderated hypofractionated regimens has not been well validated in Asian countries. The aim of this multi-institutional phase II study was to confirm the safety and the potential efficacy of moderately hypofractionated intensity-modulated radiotherapy (IMRT) with prostate-based image-guidance for Japanese patients. Methods Patients with low- or intermediate-risk localized prostate cancer were eligible. Patients with a part of high risk (having only one of the following factors, cT3a, 20 < PSA ≤ 30, or GS = 8 or 9) were also included in this trial. Hypofractionated IMRT using daily image-guided technique with prostate matching was performed with a total dose of 70 Gy in 28 fractions. Neoadjuvant hormonal therapy for 4-8 months was mandatory for patients with intermediate or high-risk prostate cancer. Results The number of patients with low, intermediate, and high-risk prostate cancer was 20, 80, and 34, respectively. The 5-year overall, biochemical failure-free, and clinical failure-free survival was 94.5%, 96.0%, and 99.2%, respectively. The 5-year biochemical failure-free survival for patients with low-, intermediate-, and high-risk disease was 94.1%, 97.4%, and 93.9%, respectively. The incidences of grade 2 gastrointestinal and genitourinary late toxicities at 5 years were 5.3% and 5.3%, respectively. There are no acute or late toxicities ≥ grade 3. Conclusion The safety and efficacy of moderately hypofractionated IMRT was confirmed in this trial among Japanese patients with prostate cancer.