Persistent bothersome urinary frequency following stereotactic body radiation therapy for clinically localized prostate cancer: rationale for prophylactic β3-agonist in men with elevated baseline international prostate symptom scores.

[INTRODUCTION] Stereotactic body radiation therapy (SBRT) for clinically localized prostate cancer has been associated with prolonged acute obstructive and irritative lower urinary tract symptoms (LUTS). Prophylactic alpha-adrenergic antagonists have been used therapeutically to prevent obstructive symptoms in patients undergoing prostate SBRT, however irritative symptoms may be better addressed with beta 3-adrenergic receptor agonists, which are shown to be safe and effective in men with overactive bladder (OAB).

[OBJECTIVE] This study retrospectively examines the pattern of bothersome urinary frequency associated with SBRT to determine which patients would have potentially benefitted from prophylactic beta 3-adrenergic receptor agonist.

[METHODS] Patients with clinically localized prostate cancer who underwent prostate SBRT (n=1676) were followed for 3 months post-treatment to evaluate for bothersome urinary frequency, which was assessed by question 4E on the EPIC-26. Answers to question 4E and tamsulosin usage were recorded at regular follow-ups to assess, and demographic factors as well as baseline prostate volume, alpha-adrenergic antagonist usage and IPSS score severity were used as modifiers.

[RESULTS] Using the IPSS questionnaire to determine baseline LUTS, most patients reported moderate urinary symptoms (53%), followed by mild (34%) and severe (13%). Patients endorsed increased irritative LUTS at 1-month post-SBRT, with similar rates of frequency at 3 months compared to baseline. Patients with moderate and severe urinary symptoms per the baseline IPSS were more likely to endorse bothersome urinary frequency at one month post SBRT (EPIC-26 Q4E; OR 2.58 and 10.2 respectively) compared to those with mild symptoms. No significant differences were found in urinary frequency between patients who used and did not use an alpha antagonist at baseline.

[CONCLUSIONS] Bothersome post-SBRT urinary frequency persists 1-month post-SBRT. Baseline LUTS predicts bothersome post-treatment urinary frequency. Prophylactic alpha-adrenergic antagonists do not protect against bothersome acute urinary frequency. This paper makes the case that urinary frequency may be better addressed with a prophylactic beta-3 agonist, like vibegron, which is designed to treat storage-related LUTS concerns.