CUA 2018: The WATER Study Clinical Results: A Subgroup Analysis of Larger Prostates from the Phase 3, Blinded, Randomized Trial of Aquablation vs. Transurethral Resection of the Prostate

Halifax, Nova Scotia ( Benign prostate hyperplasia (BPH) is one of the most common diseases treated by urologists. While the introduction of medical therapy with alpha-blockers and 5-alpha reductase inhibitors in the 1990s significantly changed the management of BPH, there remains a large and important role of surgical intervention. Endoscopic resection via transurethral resection of the prostate (TURP) remains the gold standard for surgical treatment of BPH despite numerous other treatments being introduced over the past few decades. A newly introduced treatment option for BPH is aquablation. A randomized controlled trial assessing its efficacy compared to TURP has recently been published1. Using this approach, transrectal ultrasound guidance is used to delineate a resection volume which is then treated by an “autonomously” functioning robotic apparatus.

The duration of TURP and risk of complications associated with TURP are correlated with prostate size. In this subgroup analysis of the WATER study presented as a podium presentation at the Canadian Urologic Association Annual Meeting, Paul Anderson, MD, and colleagues assessed the safety and efficacy of aquablation compared with TURP in men with prostates between 50 and 80 mL in volume.

While described in detail in the aforementioned article1, WATER is a, blinded, multicentre, phase 3 trial, men with moderate–to–severe lower urinary tract symptoms (LUTS) related to BPH were assigned to TURP using either standard electrosurgery or robotically–assisted waterjet ablation in a 1:2 ratio. In this presentation, Dr. Anderson reported on a pre–planned subgroup analysis based on prostate volume (<50 vs. ≥50 mL) using the trial’s co–primary safety and efficacy endpoint. The primary safety endpoint was the occurrence of Clavien–Dindo Grade 1 (persistent ejaculatory dysfunction, erectile dysfunction, or urinary incontinence) or Grade 2 or higher operative complications at three months. The primary efficacy endpoint was the reduction in International Prostate Symptom Score (IPSS) score at six months.

In the overall study cohort, there were 184 patients enrolled. The mean baseline IPSS score (T: 22.2 vs. A: 22.9; p=0.43), demographic profile, and mean prostate volume (T: 52 mL vs. A: 54 mL; p=0.31) were similar. Despite similar mean operative time (T: 35.5 vs. A:32.8 minutes; p=0.28), mean resection time was significantly lower in the aquablation group (28 vs. 4 minutes; p<0.0001). The primary safety endpoint (Clavien–Dindo Grade 1 persistent or Grade 2 or higher event in the first three months) occurred in 19% of aquablation subjects and 43% of TURP subjects (p<0.01). 

In the subgroup most relevant for this report, there were 99 patients with a prostate volume greater than 50 mL (T:35 vs. A:64). For men with larger prostates, changes in IPSS were greater after aquablation compared to TURP (by approximately four points; p=0.0056). While post-hoc and subject to the incumbent biases of such an approach, IPSS changes were larger with aquablation compared to TURP (by 3.7 points; p=0.0118) in men with baseline maximum flow rates (Qmax) <9 mL/sec. For men with both larger (>50 mL) baseline prostate volume and lower (<9 mL/sec) flow rates, the improvement in IPSS scores was seven points larger in aquablation compared to TURP (p<0.0001). For men with prostate size <50 mL and maximum flow rate >9 mL/sec, the change with TURP was 4.3 points larger after TURP (p=0.0963).

The authors conclude that, among men with large prostates (50–80 mL), aquablation has significantly better efficacy and safety results as compared to TURP.

Presented by: Paul Anderson, MD, Royal Melbourne Hospital, Melbourne, Australia

1. Gilling P. et al, WATER: A Double-Blind, Randomized, Controlled Trial of Aquablation® vs Transurethral Resection of the Prostate in Benign Prostatic Hyperplasia, Journal of Urology, 2018

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


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