Multi-variable models predicting specific patient-reported acute urinary symptoms after radiotherapy for prostate cancer : results of a cohort study

Purpose A prospective trial started in 2010, aiming at developing models for urinary toxicity and erectile dysfunction after radiotherapy for prostate cancer. This analysis is finalised at highlighting correlations between clinical/dosimetric factors and acute urinary specific symptoms, as measured by single questions of the International Prostate Symptom Score (IPSS). Materials/methods IPSS was prospectively collected before and at the end of radiotherapy; absolute weekly bladder dose-surface histograms (DSHw) were chosen as dosimetric descriptors. Relevant clinical factors were prospectively gathered. Backward feature selection was used to identify variables to be included in logistic models for moderate-severe (scores ≥ 4) urinary symptoms. Results Complete data of 262 patients (120 conventional fractionation, 142 hypofractionation) were available. Smoking was a strong predictor for feeling of incomplete emptying, frequency, intermittency, urgency and straining; neoadjuvant hormonal therapy and use of antihypertensive drugs were risk factors for intermittency and weak stream, respectively. The baseline score was a major predictor for all symptoms with the exception of intermittency. DSHw were correlated to increased risk of frequency, intermittency, urgency and nocturia. Most models showed moderate-high discrimination (AUC 0.60-0.79). Conclusions Smoking and other clinical and dosimetric factors predict for specific moderate-severe acute urinary symptoms; baseline condition heavily modulated the risk in most endpoints.