KEY POINTS
- Investigators retrospectively reviewed 863 consecutive patients receiving curative prostate SBRT between 2016 and 2025. Propensity matching for age, PSA, Gleason score, T stage, NCCN risk and ADT produced 530 matched patients.
- Treatment consisted of either 36.25 Gy or 40 Gy in five fractions, delivered every other day using VMAT and daily CBCT. The prespecified non-inferiority boundary was an HR of 1.40.
- Five-year event-free survival was 90.0% with 36.25 Gy versus 88.1% with 40 Gy (p=0.37). The HR for 36.25 versus 40 Gy was 0.76 (95% CI 0.42–1.39), with the upper confidence bound just below the prespecified non-inferiority margin.
- Five-year PSA recurrence-free survival was similarly high: 94.5% versus 93.2% (p=0.76). Importantly, 15% of PSA recurrences occurred after five years, supporting the need for longer observation when comparing prostate SBRT dose schedules.
- No grade ≥3 acute toxicity occurred. Across the full safety population, severe late GI/GU events were uncommon; no grade 4 toxicity occurred after 36.25 Gy, while several grade 4 GI/GU events occurred in the 40-Gy cohort. No grade 5 toxicity was reported.
- EPIC urinary irritative/obstructive scores recovered toward baseline after the initial post-treatment decline and were significantly better with 36.25 Gy at 3, 12 and 24 months. Bowel and sexual-domain scores did not differ significantly.
- The main confounding issue is substantial: 36.25 Gy was predominantly used before mid-2018, whereas 40 Gy was introduced later, and rectal-spacer use after matching remained 20.8% versus 74.0%. The apparent non-inferiority and QOL differences therefore remain hypothesis-generating rather than equivalent to a randomized dose comparison.
CLINICAL TAKEAWAY
These data provide further reassurance that 36.25 Gy in five fractions remains a highly effective prostate SBRT regimen, with no obvious disease-control advantage for 40 Gy in this cohort. They do not establish that dose escalation is unnecessary, because the comparison is strongly confounded by treatment era and spacer use.