Urinary toxicity in men treated with stereotactic body radiation therapy (SBRT) for localized prostate cancer following procedures for benign prostatic hyperplasia (BPH).

Abstract

91 Background: Patients with a history of procedures for BPH experience worse urinary toxicity following interstitial brachytherapy for localized prostate cancer. This retrospective study sought to evaluate the rates of urinary toxicity following SBRT in men with a history of procedures for BPH. Methods: Localized prostate cancer patients, treated with SBRT from August 2009 to February 2015 and a minimum follow up of 2 years, with a history of at least 1 procedure for BPH associated with a prostatic defect identified on the treatment planning MRI were evaluated. Radiotherapy was delivered in 5 fractions to a dose of 35 or 36.25 Gy using the CyberKnife system with fiducial tracking. Urinary QOL was assessed pre- and post-treatment using the International Prostate Symptom Score (IPSS) and the Expanded Prostate Cancer Index Composite (EPIC-26). Cystoscopy findings were retrospectively reviewed. Toxicities were scored using the CTCAE v4. Results: Thirty nine men with a median age of 72 years, 7 with a history of more than 1 procedure for BPH, were treated with a median follow up of 49 months. Grade 1, grade 2, and grade 3 urinary toxicity occurred in 11, 24, and 3 men, respectively; there were no grade 4 or 5 toxicities. Overall, 22 men experienced hematuria; the median time to the onset hematuria from the start of SBRT was 13 months (range 1-70). Cystoscopy was performed on 12 of these patients and bladder neck/prostatic urethra hyperemia were found in a majority of cases. Active bleeding from the bladder neck or prostatic urethra was found in 4 men. A mean baseline IPSS score of 9 did not significantly change at any point during follow up. A mean baseline EPIC-26 obstructive/irritative score of 84 significantly decreased to 76 at 1 month (p = 0.023). There was no significant change from the mean baseline EPIC-26 urinary incontinence score at any point during follow up. Conclusions: A history of procedures for BPH may lead to worse urinary quality of life and high rates of hematuria following SBRT for localized prostate cancer. Stricter urethra/bladder neck dose constraints or an alternative fractionation schedule may be required to decrease the risk of urinary toxicity.