Stereotactic body radiotherapy with or without external beam radiation as treatment for organ confined high-risk prostate carcinoma: a six year study

Background: Stereotactic Body Radiotherapy (SBRT) has excellent control rates for low-and intermediate-risk prostate carcinoma. The role of SBRT for high-risk disease remains less studied. We present long-term results on a cohort of patients with NCCN-defined high-risk disease treated with SBRT. Methods: We retrospectively studied 97 patients treated as part of prospective trial 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 = 45). 46 patients received Androgen Deprivation Therapy. Quality of life and bladder/bowel toxicity was assessed using the Expanded Prostate Index Composite (EPIC) and RTOG toxicity scale. Results: Median followup was 60 months. 6-year biochemical disease-free survival (bDFS) was 69%. On multivariate analysis, only PSA remained significant (P < 0.01) for bDFS. Overall toxicity was mild, with 5% Grade 2-3 urinary and 7% Grade 2 bowel toxicity. Use of pelvic radiotherapy was associated with significantly higher bowel toxicity (P = .001). EPIC scores declined for the first six months and then returned towards baseline. Conclusions: SBRT appears to be a safe and effective treatment for high-risk prostate carcinoma. Our data suggests that SBRT alone may be the optimal approach. Further followup and additional studies is required to corroborate our results.