94 Background: Stereotactic Body Radiotherapy (SBRT) is an emerging treatment modality with excellent control rates for low- and intermediate-risk prostate cancer. The role of SBRT for high-risk disease, however, is less studied. The standard treatment (RT) for high-risk prostate cancer entails 8-9 weeks of daily RT with long-term androgen deprivation therapy (ADT). In comparison to this, SBRT is completed in 5 sessions, and offers convenience, low toxicity, and equivalent biochemical disease control rates as standard RT in the low- and intermediate-risk setting. We now present long-term results for SBRT in a cohort of patients with high-risk disease. Methods: We evaluated patients treated from 2006-2010 with SBRT alone (n = 52) to dose of 35-36.25 Gy in 5 fractions, or pelvic radiation to 45 Gy followed by SBRT boost of 19-21 Gy in 3 fractions (n = 46). Androgen deprivation therapy was administered to 55% of patients. Quality of life and bladder/bowel toxicity was assessed using the Expanded Prostate Index Composite (EPIC) and RTOG toxicity scale at regular time intervals. Results: Median followup was 84 months. 8-year biochemical disease-free survival (bDFS) was 61.3%. On univariate analyses,PSA was significant for bDFS (p = 0.001), whereas pelvic radiation (p = 0.97), T-stage (p = 0.79), ADT (p = 0.77), Gleason score (p = 0.78) were not. On multivariate analysis, only PSA remained significant (p = 0.003) for bDFS. Overall toxicity was mild, with 5.1% Grade 2 urinary, 3% Grade 3 urinary and 7.1% Grade 2 bowel toxicity. Use of pelvic radiotherapy was associated with significantly higher bowel toxicity (p = .001). EPIC bowel and bladder scores declined for the first six months and then returned towards baseline. Conclusions: Five-treatment SBRT appears to be a safe and effective treatment for high-risk prostate carcinoma now with median 84 month follow up. The addition of pelvic radiation or ADT does not confer any bDFS benefit with this modality. Our data suggests that SBRT alone may be the optimal approach. SBRT may be a good treatment alternative to discuss particularly for patients unable to undergo ADT or unwilling to receive standard 8-9 week RT. Prospective studies are required to corroborate our results.
MP46-10 FOCAL CRYOTHERAPY FOR LOW- TO INTERMEDIATE-RISK PROSTATE CANCER: LONG TERM RESULTS AND MATCHED PAIR COMPARISON WITH ACTIVE SURVEILLANCE
