Favorable 10-year outcomes of image-guided intensity-modulated radiotherapy combined with long-term androgen deprivation for Japanese patients with nonmetastatic prostate cancer

AIM: To investigate 10-year outcomes of high-dose image-guided intensity-modulated radiation therapy (IG-IMRT) combined with long-term androgen deprivation therapy (ADT) for Japanese patients with nonmetastatic prostate cancer. METHODS: A retrospective analysis was performed on 208 Japanese patients with T1-4N0M0 prostate cancer, who underwent definitive IG-IMRT from 2006 to 2010 at our single institution. The median dose was 78 Gy (74-78) and median ADT time was 32 months (6-151). The risk stratification followed the National Comprehensive Cancer Network criteria. A biochemical relapse was defined as nadir plus 2.0 ng/mL. Toxicity was scored with the Radiation Therapy Oncology Group morbidity scale. RESULTS: The median follow-up time was 102 months. For low-, intermediate-, high-, and very-high-risk groups, the 10-year biochemical disease-free survival rates were 100%, 84%, 90%, and 72%, respectively (P = 0.008); clinical relapse-free survival rates were 100%, 100%, 100%, and 81%, respectively (P < 0.001); and cancer-specific survival rates were 100%, 100%, 100%, and 89%, respectively (P = 0.13). The independent prognostic factors influencing biochemical relapse were younger age, Gleason score ≥ 8, and radiation dose < 78 Gy in the multivariate analysis (P = 0.006, 0.014, and 0.013). The 10-year cumulative incidence of late grade 2 or higher gastrointestinal and genitourinary toxicities were 12% and 13%, respectively. No events of grade 4 or 5 were observed. CONCLUSIONS: This study suggest that high-dose IG-IMRT combined with long-term ADT is effective and implementable, leading to excellent 10-year outcomes for Japanese patients with nonmetastatic prostate cancer.