Furthering the external validity of Aquablation and implications for real-world patients

  • David-Dan Nguyen
  • Naeem Bhojani
  • Kevin C. Zorn
Letter to Editor

Dear Editor,

Despite international variance, the approval process for novel surgical devices employs various means to evaluate two key aspects of new technology: safety and efficacy. To do so, prior to full clearance, devices are assessed in a controlled experimental setting; ideally, randomized trials would be the default option in this stage [1]. Aquablation, a robotically executed, surgeon-guided, high-pressure water jet technology integrating real-time ultrasonography for the treatment of benign prostatic hyperplasia (BPH), underwent such an evaluation leading to FDA approval in December of 2017 following the WATER clinical trial (NCT02505919) that demonstrated that Aquablation was safe and efficacious in men with prostates between 30 and 80 cc [2].

However, clinical trials are limited by their own design; notably, a well-designed randomized control trial requires stringent inclusion and exclusion criteria limiting its external validity [3]. To palliate to these external validity...


Author contributions

DDN: manuscript writing/editing. NB: manuscript writing/editing and review. KCZ: manuscript writing/editing and review.

Compliance with ethical standards

Conflict of interest

NB and KCZ participated in WATER II. WATER II study data were entered into an electronic data capture system by site coordinators, were monitored, and source verified by monitors hired by the study sponsor (PROCEPT BioRobotics). No author of this letter has a conflict of interest with PROCEPT BioRobotics.

Research involving human participants and/or animals

None for this letter to the editor.

Informed consent

Not applicable for the letter to the editor.


  1. 1.
    McCulloch P, Altman DG, Campbell WB et al (2009) No surgical innovation without evaluation: the IDEAL recommendations. Lancet 374(9695):1105–1112. CrossRefPubMedGoogle Scholar
  2. 2.
    Gilling PJ, Barber NJ, Bidair M, Anderson P. Water—a double-blind randomized controlled trial of aquablation vs. transurethral resection of the prostate in benign prostatic hyperplasia. J Urol. (In press)Google Scholar
  3. 3.
    Rothwell PM (2005) External validity of randomised controlled trials: to whom do the results of this trial apply? Lancet 365(9453):82–93. CrossRefPubMedGoogle Scholar
  4. 4.
    Bach T, Giannakis I, Bachmann A et al (2018) Aquablation of the prostate: single-center results of a non-selected, consecutive patient cohort. World J Urol 2018:1–7. CrossRefGoogle Scholar
  5. 5.
    Leopold SS (2013) Words and meaning in scientific reporting: consecutive, prospective, and significant. Clin Orthop Relat Res 471(9):2731–2732. CrossRefPubMedPubMedCentralGoogle Scholar
  6. 6.
    Desai M, Bidair M, Bhojani N et al (2018) WATER II (80-150 mL) procedural outcomes. BJU Int. CrossRefPubMedGoogle Scholar
  7. 7.
    Ajib K, Mansour M, Zanaty M et al (2018) Photoselective vaporization of the prostate with the 180-W XPS-Greenlight laser: five-year experience of safety, efficiency, and functional outcomes. Can Urol Assoc J. 12(7):E318–E324. CrossRefPubMedPubMedCentralGoogle Scholar
  8. 8.
    Birkmeyer JD, Stukel TA, Siewers AE, Goodney PP, Wennberg DE, Lucas FL (2003) Surgeon volume and operative mortality in the United States. N Engl J Med 349(22):2117–2127. CrossRefPubMedGoogle Scholar
  9. 9.
    Lowrance WT, Southwick A, Maschino AC, Sandhu JS (2013) Contemporary practice patterns of endoscopic surgical management for benign prostatic hyperplasia among urologists in the United States. J Urol 189(5):1811–1816. CrossRefPubMedGoogle Scholar
  10. 10.
    Wilson LC, Gilling PJ, Williams A et al (2006) A randomised trial comparing holmium laser enucleation versus transurethral resection in the treatment of prostates larger than 40 grams: results at 2 years. Eur Urol 50(3):569–573. CrossRefPubMedGoogle Scholar
  11. 11.
    Kuntz RM, Ahyai S, Lehrich K, Fayad A (2004) Transurethral holmium laser enucleation of the prostate versus transurethral electrocautery resection of the prostate: a randomized prospective trial in 200 patients. J Urol 172(3):1012–1016. CrossRefPubMedGoogle Scholar
  12. 12.
    Ahyai SA, Gilling P, Kaplan SA et al (2010) Meta-analysis of functional outcomes and complications following transurethral procedures for lower urinary tract symptoms resulting from benign prostatic enlargement. Eur Urol 58(3):384–397. CrossRefPubMedGoogle Scholar
  13. 13.
    Yin L, Teng J, Huang C-J, Zhang X, Xu D (2013) Holmium laser enucleation of the prostate versus transurethral resection of the prostate: a systematic review and meta-analysis of randomized controlled trials. J Endourol 27(5):604–611. CrossRefPubMedGoogle Scholar
  14. 14.
    Gilling PJ, Wilson LC, King CJ, Westenberg AM, Frampton CM, Fraundorfer MR (2012) Long-term results of a randomized trial comparing holmium laser enucleation of the prostate and transurethral resection of the prostate: results at 7 years. BJU Int 109(3):408–411. CrossRefPubMedGoogle Scholar
  15. 15.
    Elshal AM, Elkoushy MA, El-Nahas AR et al (2015) GreenLight™ Laser (XPS) Photoselective vapo-enucleation versus holmium laser enucleation of the prostate for the treatment of symptomatic benign prostatic hyperplasia: a randomized controlled study. J Urol 193(3):927–934. CrossRefPubMedGoogle Scholar
  16. 16.
    Bhojani N, Nguyen D-D, Kaufman RP, Elterman D, Zorn KC (2018) Comparison of < 100 cc prostates and > 100 cc prostates undergoing aquablation for benign prostatic hyperplasia. World J Urol. CrossRefPubMedGoogle Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • David-Dan Nguyen
    • 1
  • Naeem Bhojani
    • 2
  • Kevin C. Zorn
    • 2
  1. 1.Faculty of MedicineMcGill UniversityMontrealCanada
  2. 2.Division of UrologyUniversité de Montréal Health CentreMontrealCanada

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