Stereotactic body radiotherapy for treatment of organ-confined prostate cancer: Efficacy and quality of life at 4 years.

Abstract

88 Background: The purpose of this study is to assess the efficacy and toxicity of stereotactic body radiotherapy for organ confined prostate cancer patients. Methods: Fifty T1cN0M0 prostate carcinoma patients (42 low- and 8 intermediate-risk) received 5 fractions of 7 Gy SBRT with Cyberknife to a total dose of 35 Gy delivered over 5 consecutive days. Mean patient age was 69.5 years and mean pre-treatment PSA was 5.7 ng/mL. All patients received 1500 mg of amifostine intrarectally prior to each SBRT fraction. Patients were treated to the 83%-87% contour line with 5-mm margins added to the gross tumor volume at all borders except for the rectum where a 3-mm margin was added. During treatment, 4 gold fiducial seeds were continuously tracked. Toxicity was assessed using the Radiation Therapy Oncology Group toxicity scale; biochemical failure was assessed by the Phoenix criteria, and quality of life was assessed with the Expanded Prostate Cancer Index Composite Questionnaire (EPIC). Results: At a median follow-up of 48 months (range, 46-53 months) one biochemical failure has occurred. Three patients died of intercurrent disease. The median PSA at 48 months is 0.10 ng/mL (range, 0.01-3.5 ng/mL). At 42 months, 42 of 47 patients had achieved a PSA of 0.5 ng/mL or less. Toxicity has been minimal with no grade 3+ toxicities. Actuarial 48 month rates for grade 2 urinary and rectal toxicity-free survival were 95.5% and 97.8%, respectively. Mean EPIC bowel and urinary quality of life returned to baseline by 18 months and remain at baseline values at 36 months. Of the 36 patients that were potent prior to treatment 29 (80.5%) maintained potency. Conclusions: At 48 months median follow-up the promising biochemical control, minimal toxicity and the promising potency preservation rates are highly encouraging. [Table: see text]