Background
Systematic review and meta-analysis of prospective stereotactic body radiation therapy (SBRT) studies for localized prostate cancer. 38 prospective studies, 6,116 patients treated 1999–2017 (single-institution series and multicenter trials). Goal: summarize biochemical failure-free survival (bFFS) and toxicity, providing the evidence base for SBRT across risk groups.
Interventions and follow up
Treatment: SBRT — predominantly 35–40 Gy in 5 fractions (7–8 Gy/fx), minority 7-fraction/other; CyberKnife and linac; no ADT in most low/intermediate-risk patients
Analysis: Pooled random-effects models
Primary endpoint: 5-year biochemical failure-free survival by risk group; toxicity rate
Analysis: Pooled random-effects models
Primary endpoint: 5-year biochemical failure-free survival by risk group; toxicity rate
Results
5-year bFFS, low-risk: 95.3%
5-year bFFS, intermediate-risk: 83.3%
5-year bFFS, high-risk: 70.0%
Late grade ≥3 GU toxicity: 2.0% (95% CI 1.5–2.7%)
Late grade ≥3 GI toxicity: 0.4% (95% CI 0.2–0.7%)
Erectile dysfunction: ~23% at 5 years
5-year bFFS, intermediate-risk: 83.3%
5-year bFFS, high-risk: 70.0%
Late grade ≥3 GU toxicity: 2.0% (95% CI 1.5–2.7%)
Late grade ≥3 GI toxicity: 0.4% (95% CI 0.2–0.7%)
Erectile dysfunction: ~23% at 5 years
Adverse events
GU: Pooled late grade ≥3 2.0%
GI: Pooled late grade ≥3 0.4%
Grade 4+: Low
Note: Both lower than or comparable to conventional RT historical rates; patient-reported outcomes data limited
GI: Pooled late grade ≥3 0.4%
Grade 4+: Low
Note: Both lower than or comparable to conventional RT historical rates; patient-reported outcomes data limited
Conclusions
SBRT for localized prostate cancer achieves 5-year bFFS comparable to historical dose-escalated IMRT (70–80 Gy) and brachytherapy, with low severe late toxicity. Supports SBRT as an effective, well-tolerated option across risk groups, enabling 1–2 week courses vs 7–8 weeks.
Key Limitations
Mostly single-institution observational series, subject to publication bias. Heterogeneity in dose/fractionation, technique (CyberKnife vs linac), and selection. Many early cohorts with limited follow-up; bFFS curves continue to separate beyond 5 years. Lack of standardized quality-of-life measurement. Preceded randomized HYPO-RT-PC (Widmark 2019) and PACE-B (Brand 2019), now the definitive evidence.
Clinical Context
Provided key pooled evidence supporting SBRT prior to RCT data; contributed to the 2018 ASTRO/ASCO/AUA guideline endorsement of SBRT as an option for localized prostate cancer. Subsequent randomized HYPO-RT-PC (2019) and PACE-B (2019/2024) provided Level 1 evidence. SBRT is now a standard option at experienced centers for low/intermediate-risk disease, with ongoing trials in high-risk disease with ADT.