5084 Background: To report 10 year results after image guided intensity-modulated radiotherapy (IMRT) with hypofractionated simultaneous integrated boost (SIB) in high-risk prostate cancer. Methods: Between 2007 and 2009, 97 patients with an estimated risk of lymph node metastases above 15% (Roach equation) were prospectively included in a phase II study. Patients were treated with 2-2.7 Gy to the prostate, vesicula seminalis and elective pelvic field in 25 fractions over 5 weeks with androgen deprivation therapy for 2 years. Toxicity was scored according to RTOG criteria and biochemical free survival (BFS) using the Phoenix definition. Patients were divided into three groups; very high-risk patients (VHR) according to NCCN 2015 criteria (n=50), high-risk patients (HR) (n=32), and patients with N+ disease and/or pretreatment s-PSA ≥100 (n=15). Differences were examined using Kaplan Meier estimates with log rank test. Results: Ten year BFS in the entire cohort was 63%. Metastasis-free survival (MFS) was 77% and prostate-cancer-specific-survival (PCSS) 88%. Overall survival (OS) was 69% and local failure rate was 11%. VHR vs. HR subgroups had significant different BFS; 58% vs 84% (p=0.01) respectively. MFS and PCSS in the VHR group compared to the HR group was 78% vs 91% (p=0.108) and 86% vs 97% (p=0.157) respectively. Patients with N+ and/or PSA>100 had worse outcome compared to the HR/VHR groups, but not all had treatment failure. BFS was 33% vs 68% (p=0.001), MFS 47% vs 83% (p=0.000) and PCSS 73 % vs 90% (p=0.04), respectively. Patients who reached a PSA nadir value below 0.1 (n=80) had significant better outcomes, with PCSS 93% vs 65% (p= 0.001) and BFS 74% vs 12% (p=0.000), respectively. Acute gr 2 GI and GU toxicity was observed in 27% and 40%, gr 3 GI and GU toxicity in 1% and 3%. Late gr 2 GI and GU toxicity at 3 years appeared in 3% and 4% with no gr 3 toxicity. Conclusions: High-risk prostate cancer patients treated with IMRT with SIB obtained favorable outcomes with few serious side effects. There were significant better results in the HR versus the VHR group, both better than the N+/PSA≥100 group.
EP-1362: Hypofractionated Simultaneous Integrated Boost IMRT in high risk prostate cancer – A novel approach
