Incidence of Patient-Reported Urinary Incontinence after Stereotactic Body Radiation Therapy for Clinically Localized Prostate Cancer.

254 Background: Urinary incontinence (UI) following prostate radiotherapy is a rare toxicity that adversely affects a patient’s quality of life. The potential for hypofractionated radiotherapy to increase the risk of UI was investigated. This study sought to evaluate the incidence and severity of UI following stereotactic body radiation therapy (SBRT) for prostate cancer. Methods: Between February 2008 and August 2011, 216 men with clinically localized prostate cancer were treated definitively with SBRT at Georgetown University Hospital. Patients were treated to 35 to 36.25Gy in five fractions delivered with the CyberKnife (Accuray). UI was defined as self-reported involuntary urine loss and was assessed via the UI domain of the Expanded Prostate Index Composite (EPIC)-26 at baseline and at months 1, 3, 6, 9, 12, 18, and 24. EPIC scores range from 0 to 100 with lower values representing worsening incontinence. The minimally important difference (MID) was defined as a change of one-half standard deviation from the baseline. Results: The median age was 66 with a median prostate volume of 38 cc. The median follow-up was 3.2 years. Baseline UI was common with 22.0%, 26.2%, and 3.3% of patients reporting leaking, dribbling and pad usage, respectively. At two year post treatment, 31.1%, 34.7%, and 7.1% of patients reported some degree of incontinence based on leaking, dribbling and pad usage, respectively. Average EPIC UI domain scores showed a slow decline over the first two years following treatment. At two year post treatment, the median decreased from a baseline of 92.1 to 88.0. This change was statistically (p < 0.001) but not clinically significant (MID=6.7). The proportion of men feeling that their UI was a moderate to big problem increased from 1% at baseline to 6% at two years post treatment. Conclusions: SBRT for clinically localized prostate cancer was well tolerated with UI rates comparable to conventionally fractionated radiotherapy and brachytherapy. Greater than 90% of men who were pad-free prior to treatment remained pad-free two years following treatment. Less than 10% of men felt posttreatment UI was a moderate to big problem.