CUA 2018: A Pilot Randomized–Controlled Trial of the Urodynamic Efficacy of Mirabegron for Patients with Neurogenic Lower Urinary Tract Dysfunction

Halifax, Nova Scotia ( Mirabegron has been used for many years in patients with overactive bladder. In a podium presentation at the Canadian Urologic Association Annual Meeting, Blayne Welk, MD, and colleagues presented results of a randomized-controlled trial of this agent in patients with neurogenic lower urinary tract dysfunction.

The authors recruited patients with neurogenic lower urinary tract dysfunction as a result of spinal cord injury (SCI) or multiple sclerosis (MS). Following investigations and urodynamic evaluation, patients were randomized in a double-blind fashion to mirabegron 25mg daily or placebo for 2 weeks. Patients then underwent dose-escalation to 50mg mirabegron or placebo which was then continued for eight weeks.

At the eight-week mark, patients underwent repeat investigation, including with urodynamics. The primary outcome of the analysis was urodynamic measured bladder capacity. Secondary outcomes included other UDS parameters, pad test, three–day diary, validated symptom scores, and quality of life measures. Data were analyzed in an intention-to-treat fashion using ANCOVA models to adjust for baseline values with marginal means reported.

Based on the preliminary data presented today, Dr. Welk reported on a total of 16 (nine SCI and seven MS) patients who were randomized to mirabegron and 16 (10 SCI and six MS) to placebo. At eight-week assessment of the primary outcome, there was no significant difference in urodynamic bladder capacity between mirabegron and placebo (marginal means 305 vs. 369 mL; p=0.20). 

Among the secondary outcomes, they found no significant difference in volume at first NDO (marginal means 183 vs. 133 mL; p=0.10) or peak pressure of NDO (marginal means 69 vs. 82 cmH2O; p=0.25). This is perhaps not surprising as the effect size for these values was small (<0.20). Neurogenic detrusor overactivity was documented in 12/16 mirabegron and 13/16 placebo patients and persisted in 11/16 and 12/16, respectively (p=0.66). There was no significant difference in pad weights or voiding diary. Mirabegron therapy did result in a significantly lower symptom burden (total Neurogenic Bladder Symptom Score marginal mean 29 vs. 34; p=0.047), however, quality of life scores were similar.

The authors concluded that among patients with neurogenic lower urinary tract dysfunction due to SCI or MS, mirabegron may improve patient symptoms, however, there was no significant improvement in UDS parameters, and observed trends were associated with only small effect sizes. However, this represents a very small cohort of patients and mirabegron has been previously demonstrated to be efficacious in patients with overactive bladder. Further, while neurogenic lower urinary tract dysfunction may be associated with upper tract deterioration, the primary indication for intervention is symptomatic. Thus, improvements in patient symptoms should not be underestimated in this otherwise “negative” randomized controlled trial.

Presented by: Blayne Welk, MD, MSc, FRCSC, Surgery, Western University, London, ON, Canada

Co-authors: Duane Hickling4, Mary McKibbon1, Sidney Radomski2, Karen Ethans3
1Surgery, Western University, London, ON, Canada; 2Surgery, University of Toronto, Toronto, ON, Canada; 3Internal Medicine, University of Manitoba, Winnipeg, ON, Canada; 4Surgery, University of Ottawa, Ottawa, ON, Canada

Written by: Christopher J.D. Wallis, Urology Resident, University of Toronto, Twitter: @WallisCJD at the 73rd Canadian Urological Association Annual Meeting - June 23 - 26, 2018 - Halifax, Nova Scotia