Prognostic Factors in High-Risk Prostate Cancer after Carbon-Ion Radiotherapy Combined with Long-Term Androgen Deprivation Therapy

Purpose: To determine the prognostic factors for biochemical recurrence (BR) and mortality in patients with high-risk localized prostate cancer after carbon-ion radiotherapy (CIRT) combined with long-term androgen deprivation therapy (LTADT).Methods and Materials: A total of 1247 patients were enrolled in three phase II clinical trials of fixed-dose CIRT between 2000 and 2013. Excluding T4 disease, 614 patients received CIRT combined with LTADT for high- or very-high-risk disease, according to the National Comprehensive Cancer Network (NCCN) classification system. Results: Median follow-up time was 78.7 months, and 5-year rates of BR-free, prostate cancer-specific survival, and overall survival were 90.4% (95% confidence interval [CI]: 87.6 - 92.7), 98.5% (95% CI: 97.2 - 99.2), and 94.7% (95% CI: 92.8 - 96.5), respectively. T3a/b disease, Gleason score (GS) 9-10, percentage of positive biopsy cores (PPCs) > 75%, and age > 75 years had a significant impact on BR. Moreover, patients with T3b disease, GS 9-10, and PPCs > 75% had significantly higher prostate cancer-specific mortality (p = 0.007, p = 0.009, and p = 0.015, respectively) and overall mortality (p = 0.035, p = 0.025, and p 75% should be considered to have very-high-risk disease requiring a new treatment strategy.the 56th Annual Conference of the Particle Therapy Co-operative Group (PTCOG56