Transurethral convective water vapor as a treatment for lower urinary tract symptomatology due to benign prostatic hyperplasia using the Rezūm® system: evaluation of acute ablative capabilities in the human prostate

Abstract

BackgroundThe purpose of this study was to assess the acute ablative characteristics of transurethral convective water vapor (steam) using the Rezūm® system in men with benign prostatic hyperplasia through histologic and radiographic studies.MethodsSeven patients were treated with transurethral intraprostatic injections of sterile steam under endoscopic visualization followed by previously scheduled adenectomies. The extirpated adenomas were grossly examined followed by whole mount sectioning and staining with triphenyl-tetrazolium chloride (TTC) to evaluate thermal ablation. Histology was performed after hematoxylin and eosin staining on one prostate. After review of results from the first patient cohort, an additional 15 patients with clinical benign prostatic hyperplasia were treated followed by gadolinium-enhanced magnetic resonance imaging (MRI) at one week.ResultsIn the first patient cohort, gross examination of TTC-stained tissue showed thermal ablation in the transition zone. In addition, there was a distinct interface between viable and necrotic prostatic parenchyma. Histopathologic examination revealed TTC staining-outlined necrotic versus viable tissue. Gadolinium-enhanced MRIs in the cohort of 15 patients demonstrated lesion defects in all patients at 1 week post-procedure. Coalesced lesions were noted with a mean (± standard deviation) lesion volume of 9.6±8.5 cm3. The largest lesion volume was 35.1 cm3. Ablation using vapor was rapid and remained confined to the transition zone, consistent with the thermodynamic principles of convective thermal energy transfer.ConclusionThermal ablation was observed in all specimens. The resulting coalescing ablative lesions, as seen on MRI, were confined to the transition zone. These studies confirm the ablative capabilities of vapor, validate the thermodynamic principles of convective heating, and allow for further clinical studies.

Two-year results after convective radiofrequency water vapor thermal therapy of symptomatic benign prostatic hyperplasia

“…The procedure was performed utilizing the Rezūm System previously described in detail 10–13. Briefly, water vapor thermal energy is created with RF current against an inductive coil heater in the handle of the device.…”

“…Convective RF water vapor energy (Rezūm System; NxThera, Inc., Maple Grove, MN, USA) was introduced as a minimally invasive, radiofrequency thermal energy-based treatment, designed to convectively deliver sterile water vapor, or steam for targeted ablation limited to the transition and central zones in men with clinical BPH 10–12. The objective of this report was to assess the 2-year clinical outcomes in the first patients treated with this new technology.…”

Rezum water vapour therapy for benign prostatic hyperplasia

“…Several other studies have reported similar improvements in LUTS due to BPH without a negative impact on sexual function at 1-2 years. 12,13 Early results from the UK were reported at the British Association of Urological Surgeons meeting in 2018 and are due to be presented at the European Association of Urology meeting in 2019. Rezum treatments in the UK have also received positive feedback from patients (see Box 1).…”

<div>Perspective on the Rezūm^&reg; System: a minimally invasive treatment strategy for benign prostatic hyperplasia using convective radiofrequency water vapor thermal therapy</div>

“…Because vapor has mass and is physically less dense than the compartmental barriers of the prostate (surgical capsule, true capsule, urethra, bladder neck, and external sphincter), it travels through the interstices between cells, remaining within the injected targeted prostate zone until it encounters boundaries (e.g., tissue planes between prostate zones). This has been metaphorically likened to “the way wind blows against a sail without penetrating” 9. No thermal effects have been shown to occur outside of the prostate or in the peripheral zone when the transition zone (TZ) is targeted.…”

“…MRI scans in these pilot studies were conducted at the three centers, and data were analyzed by an independent urologist (Biomedical Imaging Resource; Mayo Clinic, Rochester, MN, USA). Three-dimensional (3D) volume renderings allowed visualization of thermal lesions in relation to prostate zonal anatomy and lesion resolution after the water vapor thermal therapy 9,17. The pilot study thermal treatment procedure evolved with slight modifications to optimize water vapor delivery, dosimetry, and endoscopic technique based on characterization of the ablative lesions with MRI, time course to resolution, and changes in prostate volume.…”