Baseline International Prostate Symptom Score identifies risk of late genitourinary toxicity after hypofractionated prostate radiotherapy: TROD 09-003 study

Abstract

Background: Although moderate hypofractionation is widely adopted for localized prostate cancer, predictors of late genitourinary (GU) toxicity remain largely dose-centric. This study evaluated whether baseline urinary symptom burden, assessed by the International Prostate Symptom Score (IPSS), independently identifies the risk of late GU toxicity after hypo-fractionated prostate radiotherapy beyond conventional bladder dosimetry. Methods: This multi-institutional retrospective study included 156 patients with localized prostate cancer treated with definitive hypofractionated external beam radiotherapy. Acute and late GU toxicities were graded using radiation therapy oncology group (RTOG) criteria. Univariable and multivariable logistic regression models were used to assess associations between baseline IPSS, bladder dosimetric parameters and toxicity outcomes. Results: With a median follow-up of 42 months, late-grade >= 2 GU toxicity occurred in 3.7% of patients. In multivariable analysis adjusting for age and bladder dosimetry, baseline IPSS was the only independent predictor of late GU toxicity (adjusted odds ratio 1.11 per point increase; 95% confidence interval, 1.04-1.19; p = 0.002). This association persisted among patients who met accepted bladder dose-volume constraints. Conclusions: Baseline IPSS independently identifies patients at increased risk of late GU toxicity after hypofractionated prostate radiotherapy and provides clinically meaningful prognostic information beyond conventional dosimetric parameters. Rather than serving as a contraindication, elevated baseline IPSS represents a clinically actionable marker to support individualized risk stratification, treatment planning, patient counselling and function-informed treatment delivery