Top Line: Increased toxicity is why many continue to shy away from prostate ultra-hypofractionation as the go-to.
The Study: This systematic review pools phase 3 randomized trials (n=32) comparing conventionally fractionated radiation with moderately hypofractionated radiation (MHRT) and/or ultra-hypofractionated radiation (aka SBRT) for localized prostate cancer. Late grade 2+ GU adverse events remained steady across isodose and dose-escalated MHRT. SBRT introduced a familiar wrinkle—a delayed GU “flare” at 12–24 months—driving higher cumulative GU adverse events at 5 years. As always, worse baseline urinary function consistently predicted late GU events after both MHRT and SBRT. On the GI side, both MHRT and SBRT increased acute grade 2+ adverse events in several trials but this largely did not translate into higher late events, except in select studies with longer follow-up. What we all really care about are mitigation strategies: motion management enabling margin reduction—particularly with real-time fiducial tracking (e.g., CyberKnife or Calypso) or cine-MRI—cut grade 2+ events by roughly half in SBRT cohorts. Another less-intensive option to manage motion is minimizing table and beam-on time (e.g., with FFF beams and/or VMAT) to preclude intrafraction prostate drift.
TBL: Ultra-hypofractionation of prostate radiation likely requires sophisticated motion management with associated margin reduction in order to off-set increased risk of GU adverse events. | Guevelou, Prostate Cancer Prostatic Dis 2025
The Study: This systematic review pools phase 3 randomized trials (n=32) comparing conventionally fractionated radiation with moderately hypofractionated radiation (MHRT) and/or ultra-hypofractionated radiation (aka SBRT) for localized prostate cancer. Late grade 2+ GU adverse events remained steady across isodose and dose-escalated MHRT. SBRT introduced a familiar wrinkle—a delayed GU “flare” at 12–24 months—driving higher cumulative GU adverse events at 5 years. As always, worse baseline urinary function consistently predicted late GU events after both MHRT and SBRT. On the GI side, both MHRT and SBRT increased acute grade 2+ adverse events in several trials but this largely did not translate into higher late events, except in select studies with longer follow-up. What we all really care about are mitigation strategies: motion management enabling margin reduction—particularly with real-time fiducial tracking (e.g., CyberKnife or Calypso) or cine-MRI—cut grade 2+ events by roughly half in SBRT cohorts. Another less-intensive option to manage motion is minimizing table and beam-on time (e.g., with FFF beams and/or VMAT) to preclude intrafraction prostate drift.
TBL: Ultra-hypofractionation of prostate radiation likely requires sophisticated motion management with associated margin reduction in order to off-set increased risk of GU adverse events. | Guevelou, Prostate Cancer Prostatic Dis 2025