Nomograms to predict late urinary toxicity after prostate cancer radiotherapy

Abstract

To analyze late urinary toxicity after prostate cancer radiotherapy (RT): symptom description and identification of patient characteristics or treatment parameters allowing for the generation of nomograms. Nine hundred and sixty-five patients underwent RT in seventeen French centers for localized prostate cancer. Median total dose was 70 Gy (range, 65-80 Gy), using different fractionations (2 or 2.5 Gy/day) and techniques. Late urinary toxicity and the corresponding symptoms (urinary frequency, incontinence, dysuria/decreased stream, and hematuria) were prospectively assessed in half of the patients using the LENT-SOMA classification. Univariate and multivariate Cox regression models addressed patient or treatment-related predictors of late urinary toxicity (≥grade 2). Nomograms were built up, and their performance was assessed. The median follow-up was 61 months. The 5-year (≥grade 2) global urinary toxicity, urinary frequency, hematuria, dysuria, and urinary incontinence rates were 15, 10, 5, 3 and 1 %, respectively. The 5-year (≥grade 3) urinary toxicity rate was 3 %. The following parameters significantly increased the 5-year risk of global urinary toxicity (≥grade 2): anticoagulant treatment (RR = 2.35), total dose (RR = 1.09), and age (RR = 1.06). Urinary frequency was increased by the total dose (RR = 1.07) and diabetes (RR = 4). Hematuria was increased by anticoagulant treatment (RR = 2.9). Dysuria was increased by the total dose (RR = 1.1). Corresponding nomograms and their calibration plots were generated. Nomogram performance should be validated with external data. The first nomograms to predict late urinary toxicity but also specific urinary symptoms after prostate RT were generated, contributing to prostate cancer treatment decision.