(P075) Stereotactic Body Radiotherapy With and Without Pelvic Radiotherapy for Organ-Confined High-Risk Prostate Cancer

April 15, 2014

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 National Comprehensive Cancer Network (NCCN)-defined high-risk disease treated with SBRT.

Alan J. Katz, MD, JD, Josephine Kang, MD, PhD; Long Island Radiation Therapy; Flushing Radiation Oncology

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 National Comprehensive Cancer Network (NCCN)-defined high-risk disease treated with SBRT.

Methods: We studied 97 patients treated from 2006–2010 with SBRT alone (n = 52) to dose of 35–36.25 Gy in five fractions or pelvic radiation to 45 Gy followed by SBRT boost of 19–21 Gy in three fractions (n = 45). Forty-six patients received androgen deprivation therapy (ADT). Quality of life and bladder/bowel toxicity were assessed using the Expanded Prostate Index Composite (EPIC) and Radiation Therapy Oncology Group (RTOG) toxicity scale.

Results: Median follow-up was 60 months. Six-year actuarial biochemical disease-free survival (bDFS) was 69%. On Cox regression multivariate analysis, using prostate-specific antigen (PSA), T-stage, Gleason score, pelvic radiotherapy, and ADT as pretreatment variables, only PSA was a significant (P < .01) predictor for bDFS. Overall toxicity was mild, with 5% grade 2–3 urinary toxicity 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 6 months and then returned toward baseline.

Conclusions: SBRT appears to be a safe and effective treatment for high-risk prostate carcinoma. Our data suggest that SBRT alone, without pelvic radiotherapy or ADT, may be the optimal approach. Further follow-up and additional studies are required to corroborate our results.