Treatment outcomes and late toxicities of intensity-modulated radiation therapy for 1091 Japanese patients with localized prostate cancer

Abstract Aim This study aimed to evaluate the treatment result of intensity-modulated radiation therapy (IMRT) in a large number of Japanese patients with prostate cancer. Background A total of 1091 patients with localized prostate cancer were recruited between March 2006 and July 2014. The patients were stratified into low- ( n  = 205 [18.8%]), intermediate- ( n  = 450 [41.2%]), high- ( n  = 345 [31.6%]), and very high-risk ( n  = 91 [8.3%]) groups according to the National Comprehensive Cancer Network classification. All patients were irradiated via IMRT at a dose of 74–78 Gy with or without androgen-deprivation therapy. The mean follow-up period was 50 months (range, 2–120 months). Results The biochemical failure-free rate (BFFR), the clinical failure-free rate, and the overall survival rate at the 5-year follow-up for all patients was 91.3%, 96.2%, and 99.1%, respectively. In univariate analysis, the prostate-specific antigen (PSA) levels (≤20 vs. >20 ng/ml) were significantly correlated with BFFR. A trend toward higher BFFR was noted in patients with a Gleason score (GS) of ≤7 than in patients with GS ≥8. In multivariate analysis, only PSA (≤20 vs. >20 ng/ml) was significantly correlated with BFFR. The cumulative incidence rate of gastrointestinal and genitourinary toxicity (≥grade 2) at the 5-year follow-up was 11.4% and 4.3%, respectively. Conclusions The findings of this study indicate that IMRT is well tolerated and is associated with both good long-term tumor control and excellent outcomes in patients with localized prostate cancer.