A post hoc analysis of the phase III PACE-B trial examines predictors of late grade 2+ GU events following ultra-hypofractionationated prostate radiation. The clear winner was neither urethral nor bladder dosimetry—it was baseline urinary function. A higher baseline International Prostate Symptom Score (IPSS) independently predicted higher odds of late GU events in a continuous manner, with an exploratory threshold identifying IPSS >11 as a watershed for substantially higher risk. Baseline urinary medication use and acute grade ≥2 GU toxicity also predicted persistent urinary side effects, reinforcing the concept that ultra-hypofractionation may amplify pre-existing lower urinary tract dysfunction rather than create it de novo. On the other hand, no consistent association emerged between planned dose to the urethra, bladder trigone, or bladder dose-volume parameters and late toxicity. Ultimately, baseline IPSS may be the most practical precision medicine tool for ultra-hypofractionation patient selection. | Shelan, Transl Androl Urol 2026
