Objective: To report 5-yr efficacy, toxicity, and quality-of-life (QOL) outcomes of a novel 4-d SBRT regimen.
Design, setting, and participants: This was a single-arm prospective phase 2 trial involving 259 patients with low- or intermediate-risk PC treated at 18 US centers from December 2007 to February 2012. The median follow-up was 5 yr (interquartile range 37–85 mo).
Intervention: SBRT with 38 Gy in four fractions; radiation plans mimicked HDR brachytherapy dosimetry.
Outcome measurements and statistical analysis: We measured freedom from biochemical recurrence (BCR) and assessed toxicities using the Common Terminology Criteria for Adverse Events v3.0 and QOL using the Expanded Prostate Cancer Index Composite.
Results and limitations: The 5-yr BCR-free rates were 100% and 88.5% for patients with low- and intermediate-risk PC, respectively. The cumulative 5-yr grade 2, 3, and 4 toxicity rates were 12.4%, 1.9%, and 0.4% for urinary, and 3.4%, 0%, and 0% for gastrointestinal toxicities, respectively. The median baseline prostate-specific antigen (PSA) level of 5.12 ng/ml decreased to 0.1 ng/ml by ≥42 mo. QOL scores decreased at 1 mo but returned to baseline by 6 mo, with a later decline (≥24 mo) in the urinary continence domain (pad use was 2% at baseline and 10% at 5 yr), and lower sexual potency over time. Comparative outcomes versus other types of radiotherapy are difficult because the trial was not randomized.
Conclusions: This regimen yields a high rate of BCR-free survival, with a very low median PSA nadir suggesting prostate ablation. For properly selected patients with low- or intermediate-risk PC who choose SBRT, this treatment regimen is effective.
Patient summary: This potent four-treatment stereotactic body radiotherapy regimen appears to be effective for patients with early prostate cancer.
Phase 2 Multicenter Trial of Heterogeneous-dosing Stereotactic Body Radiotherapy for Low- and Intermediate-risk Prostate Cancer: 5-year Outcomes
Fuller, Donald B. et al. ePub ahead of print.