Solifenacin Succinate for Treatment of Urinary Toxicity Occurring During Radiotherapy of Prostatic Cancer

A multicenter Phase III, randomized, double-blinded, parallel group placebo-controlled study. 2 groups: * Control arm = pts. with placebo * Experimental arm = pts. with Solifenacin succinate 5 mg - Vesicare® All patients with an OAB sub-score using the USP scale greater to 5 during prostate cancer radiotherapy will be included, receiving either a placebo or Solifenacin succinate (5mg) for duration of 3 months. The randomization will be stratified on the radiotherapy dose (1 to 40 Gy or 40 to 70/80 Gy). Screening: For all patients, OAB items of the USP scale will be completed before each standard weekly assessment during prostate radiotherapy. Patients who reach an OAB sub-score greater to 5 will be addressed to an urologist in order to confirm absence of Qmax \< 10ml/sec at initial assessment, or post-void residual urine \> 100 milliliter (ml). Inclusion \& treatment: A week at most after pre-screening, patients will be randomized to receive either Vesicare®-5mg or a placebo. In both study arms, the treatment should be continued for 3 months. Follow-up: The radiation oncologist will perform patients' follow-up for the study at the treatment initiation, 6 weeks and 3 months after start of the treatment (Vesicare or placebo). The questionnaires for the evaluation of OAB syndrome, acute urinary toxicity and quality of life should be completed for each follow-up visit. The voiding diary will be completed during 3 days before (or if not, 3 days after) all the evaluation times. An urologist will perform an uroflowmetry and a post-voiding echography (or a bladder scan) before initiation of the treatment, and after 6 weeks of treatment. Statistics and sample size PATIENTS ENROLMENT 70 patients will be included (considering 66 patients completing the full study) within 3 recruitment centers