Abstract
PurposeHypofractionated, stereotactic body radiotherapy (SBRT) is an emerging treatment approach for prostate cancer. We present the outcomes for low-risk prostate cancer patients with a median follow-up of 5 years after SBRT.Method and MaterialsBetween Dec. 2003 and Dec. 2005, a pooled cohort of 41 consecutive patients from Stanford, CA and Naples, FL received SBRT with CyberKnife for clinically localized, low-risk prostate cancer. Prescribed dose was 35-36.25 Gy in five fractions. No patient received hormone therapy. Kaplan-Meier biochemical progression-free survival (defined using the Phoenix method) and RTOG toxicity outcomes were assessed.ResultsAt a median follow-up of 5 years, the biochemical progression-free survival was 93% (95% CI = 84.7% to 100%). Acute side effects resolved within 1-3 months of treatment completion. There were no grade 4 toxicities. No late grade 3 rectal toxicity occurred, and only one late grade 3 genitourinary toxicity occurred following repeated urologic instrumentation.ConclusionFive-year results of SBRT for localized prostate cancer demonstrate the efficacy and safety of shorter courses of high dose per fraction radiation delivered with SBRT technique. Ongoing clinical trials are underway to further explore this treatment approach.
Highlights
Prostate cancer is thought to have unique radiobiology, characterized by a low a/b ratio relative to surrounding normal tissues [1,2]
Five-year results of Stereotactic body radiotherapy (SBRT) for localized prostate cancer demonstrate the efficacy and safety of shorter courses of high dose per fraction radiation delivered with SBRT technique
Recent multi-institutional findings reported by Martinez et al for early stage prostate cancer show a 5-year biochemical disease-free survival of about 90% for HDR brachytherapy, which is comparable to their own lowdose-rate (LDR) brachytherapy outcomes, with lower late toxicity levels [5,6,7]
Summary
Prostate cancer is thought to have unique radiobiology, characterized by a low a/b ratio relative to surrounding normal tissues [1,2]. A growing body of evidence from clinical studies using hypofractionated radiation provides support that the a/b ratio for prostate cancer is lower than that for the bladder and rectum, and that a therapeutic gain could be achieved using fewer, high-dose fractions (see reviews by Dasu [3] and Macias and Biete [4]). High-dose-rate (HDR) brachytherapy can deliver radiation to a tightly constrained treatment volume using large doses per fraction. Recent multi-institutional findings reported by Martinez et al for early stage prostate cancer show a 5-year biochemical disease-free survival of about 90% for HDR brachytherapy, which is comparable to their own lowdose-rate (LDR) brachytherapy outcomes, with lower late toxicity levels [5,6,7]. Innovations in image-guidance technology, the ability to automatically correct for the movement of the prostate during treatment, and delivery of highly-conformal beam profiles have greatly enhanced the capability of delivering high dose fractions to a well-defined target, with sharp dose fall-off towards the bladder and rectum [16,17,18]
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