Relationships between bladder dose-volume/surface histograms and acute urinary toxicity after radiotherapy for prostate cancer.

BACKGROUND AND PURPOSE: DUE01 is an observational study aimed at developing predictive models of genito-urinary toxicity of patients treated for prostate cancer with conventional (1.8-2Gy/fr, CONV) or moderate hypo-fractionation (2.35-2.7Gy/fr, HYPO). The current analysis focused on the relationship between bladder DVH/DSH and the risk of International Prostate Symptoms Score (IPSS)⩾15/20 at the end of radiotherapy. MATERIALS AND METHODS: Planning and relevant clinical parameters were prospectively collected, including DVH/DSH, LQ-corrected (DVHc/DSHc) and weekly (DVHw/DSHw) histograms. Best parameters were selected by the differences between patients with/without IPSS⩾15/20 at the end of radiotherapy. Logistic uni- and backward multi-variable (MVA) analyses were performed. RESULTS: Data of 247 patients were available (CONV: 116, HYPO: 131). Absolute DVHw/DSHw and DVHc/DSHc predicted the risk of IPSS⩾15 at the end of radiotherapy (n=77/247); an MVA model including baseline IPSS, anti-hypertensive, T stage, the absolute surface receiving ⩾8.5Gy/week and ⩾12.5Gy/week was developed (AUC=0.78, 95% CI: 0.72-0.83). Similar AUC values were found if replacing DSHw with DVHw/DVHc/DSHc parameters. The impact of dose-volume/surface parameters remained when excluding patients with baseline IPSS⩾15 and in HYPO. IPSS⩾20 at the end of radiotherapy (n=27/247) was mainly correlated to baseline IPSS and T stage. CONCLUSIONS: Although the baseline IPSS was the main predictor, constraining v8.5w<56cc and v12.5w<5cc may significantly reduce acute GU toxicity.