Nomograms to predict late urinary toxicity after prostate cancer radiotherapy.

53 Background: Tools are needed to predict toxicity after prostate cancer treatment. The objective of the study was to analyze late urinary toxicity after prostate cancer radiotherapy (RT) by symptom description and identification of patient characteristics or treatment parameters allowing for the generation of nomograms. Methods: 965 patient received a median total dose of 70 Gy (range, 65-80 Gy) for localized prostate cancer, using different fractionations (2 or 2.5 Gy/day) and RT techniques. Medical history was recorded. Late urinary toxicity was assessed, prospectively in half of the patients, using the CTCAE v3 classification: urinary frequency, incontinence, bleeding and retention (dysuria). Patients or treatment related predictors of late urinary toxicity (> grade 2) were identified by Univariate and multivariate Cox regression models. Nomograms were built up and their performance were assessed. Results: The median follow-up was 61 months. The 5-year (≥grade 2) global urinary toxicity, urinary freq...