Abstract
Purpose:
To evaluate outcomes after water vapor thermal therapy (WVTT) for benign prostatic hyperplasia (BPH), stratified by varying degrees of median lobe (ML) protrusion.
Patients and Methods:
We enrolled men aged ≥45 years with BPH who underwent WVTT from July 2020 to September 2023. Inclusion criteria were an estimated prostate volume of 30–80 cc, International Prostate Symptom Score (IPSS) ≥12, and maximum urinary flow rate <16 mL/sec. ML protrusion was assessed using ultrasound (with bladder volume ≥250 cc) and flexible cystoscopy; the average of both measurements was used to classify ML protrusion into <5 mm, 5–10 mm, and >10 mm. Primary outcomes included postoperative complications such as surgical retreatment, acute urinary retention (AUR), and urinary tract infections (UTIs).
Results:
With a median follow-up of 29.1 months (range: 24–36), improvements in lower urinary tract symptoms (LUTS) were similar across all groups, with consistent symptom reduction (Δ = −13) in both obstructive and irritative IPSS components. Rates of AUR and UTIs showed no significant variation across groups: AUR (no ML 9.5%; <5 mm 8.7%; 5–10 mm 12%; >10 mm 17%; p = 0.7) and UTI (no ML 8.4%; <5 mm 4.3%; 5–10 mm 9.3%; >10 mm 8.3%; p = 0.8). Despite comparable preoperative characteristics, surgical retreatment rates varied significantly with ML protrusion: no ML (3.2%), <5 mm (4.3%), 5–10 mm (14%), and >10 mm (21%) (p = 0.007), highlighting increased retreatment risk associated with greater ML protrusion.
Conclusions:
WVTT effectively relieves LUTS across all ML configurations. However, patients with greater ML protrusion may face a higher risk of retreatment, likely because of increased bladder neck and urethral involvement. These findings suggest that detailed ML assessment can aid in patient counseling and stratification.
Keywords
Introduction
Benign prostatic hyperplasia (BPH) is the most common cause of lower urinary tract symptoms as a result of bladder outlet obstruction.1,2 BPH prevalence increases with age, affecting approximately 15% of men in their 40s and rising to 40% in their 70s. 3 Transurethral resection of the prostate (TURP) remains the most frequently utilized method for BPH treatment given its efficacious therapeutic approach. 4 However, it is not exempt from significant morbidity and complications, including incontinence, urethral stricture, and bladder neck stenosis.5,6 A diverse range of minimally invasive surgical techniques are now available for treating BPH, focusing on reducing morbidity and enhancing patient experience.
The water vapor thermal therapy (WVTT) system received Food and Drug Administration approval in 2015 and treats BPH by ablating obstructive prostatic tissue using the convective heat energy of water vapor. 7 The pivotal 5-year study for WVTT demonstrated substantial improvements in lower urinary tract symptoms (LUTS), including a 48% reduction in the International Prostate Symptom Score (IPSS) and a 44% increase in peak urinary flow rate. Notably, the treatment preserved sexual function, had a low surgical retreatment rate of 4.4%, and effectively treated the median lobe (ML) in 31% of cases. 8 McVary and colleagues concluded that the inclusion of patients with obstructive median tissue underscores the adaptability of WVTT, effectively targeting both lateral and central zone tissues, including the ML. 8
It is important to recognize that the presence of a ML is not a simple binary consideration; instead, there are various anatomical categorizations based on the degree of intravesical protrusion into the bladder lumen. Evidence is limited regarding how varying levels of intravesical protrusion (IPP) of the ML influence the outcomes of WVTT. Although Boston Scientific and NxThera, the developers of the WVTT system, clearly state that the therapy is effective for prostatic enlargements involving the ML, there is an absence of data on how different degrees of IPP impact Rezum therapy outcomes. Our study aims to fill this gap by examining the relationship between IPP and the incidence of common post-WVTT complications, such as urinary tract infections (UTIs), acute urinary retention (AUR), and retreatment rates. In addition, our research will shed light on how the specific anatomical configurations of the ML correlate with the success of WVTT.
Patients and Methods
Study design and patient enrollment
We prospectively enrolled male patients aged 45 years or older with BPH who underwent WVTT between July 2020 and September 2023. Symptomatic BPH was diagnosed in patients based on an elevated IPSS (≥12), estimated prostate volume (EPV) of 30 to 80 cc, and maximum urinary flow rate (Qmax) <16 mL/sec. Although a Qmax less than 10 mL/s is associated with a 90% likelihood of obstruction, and a Qmax between 10 and 14 mL/s corresponds to a 67% likelihood, a Qmax greater than 15 mL/s is associated with only a 30% chance of obstruction.9,10 By selecting a Qmax threshold of <16 mL/s for patient enrollment, the study aims to include a broader spectrum of patients who are likely to benefit from the intervention, including those with mild-to-moderate obstruction. Exclusion criterion included any history of prior prostate operation or prostate cancer.
Patients were eligible for WVTT if they had persistent or bothersome LUTS despite at least 6 weeks of α-blocker therapy, intolerance to medical therapy, or expressed preference for definitive treatment. Of note, 14% of patients in our cohort had not received prior medical therapy, primarily because of medication intolerance or early desire for procedural intervention. Patients with catheter-dependent urinary retention were excluded from this study. Chronic use of anticoagulants was not considered an exclusion criterion. As per institutional protocol, these patients underwent WVTT using individualized perioperative bridging strategies with low-molecular weight heparin or temporary discontinuation based on thrombotic risk. WVTT was offered to patients with an EPV of 30–80 cc based on ultrasound or MRI, in line with manufacturer recommendations and clinical judgment.
Medical therapy for BPH was typically discontinued at the time of the procedure. During follow-up, resumption of α-blockers was considered for patients experiencing persistent or bothersome symptoms, based on physician judgment and patient-reported outcomes.
The study protocol was reviewed and approved by the Comité de Ética de Clínica Las Condes, Santiago, Chile. Registration at ClinicalTrials.gov is not required for prospective studies conducted in Chile. Informed consent was obtained from all participants.
Treatment procedure
All procedures were performed by a single fellowship-trained endourologist under sedation anesthesia. Preoperative prostate measurements were obtained using endoscopic prostate measurement. ML protrusion was categorized as <5 mm, 5–10 mm, or >10 mm, based on the average of ultrasound (with a bladder volume of at least 250 cc) and flexible cystoscopy measurements.
To accurately assess and differentiate true ML protrusion from lateral lobe encroachment, we used a standardized preoperative approach combining dynamic transrectal ultrasound (TRUS) and flexible cystoscopy. Dynamic TRUS was performed with a bladder volume of ≥250 mL to optimize visualization, measuring the vertical distance from the bladder neck to the apex of the protruding tissue on sagittal images. Flexible cystoscopy corroborated these findings, identifying the ML as a midline structure and quantifying its protrusion using calibrated endoscopic markings. To minimize interobserver variability, both measurements were performed by a single fellowship-trained endourologist, and their mean value was recorded as the definitive ML protrusion.
The number of water vapor injections was determined intraoperatively based on prostate size and ML characteristics. Injections were placed at 1 cm intervals from the bladder neck to the verumontanum. For patients with an ML, injections were performed at a 45° angle from lateral to medial. The standard approach involved two injections, one from each side of the ML. However, in cases where the ML appeared less bulky (IPP 1) and an elevated bladder neck was observed intraoperatively, the surgeon performed a single injection based on clinical judgment. Although the recommended technique is two injections, this adjustment was made for patients with a nonbulky ML and an elevated bladder neck.
Postprocedurally, a urethral catheter was placed and typically removed after 5 days for patients who received four or fewer injections and after 7 days for those who received more than four injections. A trial without catheter (TWOC) was typically performed on postoperative day 5 or 7, depending on the number of water vapor injections. AUR was defined as inability to void adequately after catheter removal, necessitating re-catheterization. Patients who developed AUR were managed with re-catheterization and reattempted TWOC 48 to 72 hours later, often with the addition of an α-blocker if not already prescribed.
Patients were also given catheter valve training and a 10-day course of anti-inflammatory medications, including cyclooxygenase-2 inhibitors and nonsteroidal anti-inflammatory drugs.
Follow-up and data collection
Patients were typically reviewed at 6 weeks and at 3, 6, 12, 24, and 36 months postoperatively. Data collected included patient demographics, EPV, postvoid residual volume (PVR), prostate-specific antigen (PSA), and symptom scores (IPSS, quality of life [QoL] score). The number of patients available for follow-up as well as detailed IPSS and QoL scores at each postoperative time point are summarized in Table 2. Prostate volume was assessed using TRUS in all patients. Multiparametric prostate MRI was performed in a subset of patients who were concurrently being evaluated for prostate cancer or had borderline-large glands (>70 cc) to aid in treatment planning. In cases where both imaging modalities were available, ultrasound measurements were used for consistency. The number of patients receiving each imaging modality and corresponding median volumes are reported in Table 1.
Baseline Characteristics of Rezum Patients by Median Lobe Protrusion
Mean (SD); n (%).
Kruskal–Wallis rank sum test; Fisher’s exact test.
International Prostate Symptom Score.
Quality of Life.
Postvoid residual volume.
BPH = benign prostatic hyperplasia; SD = standard deviation.
Primary outcomes assessed were retreatment rates, AUR, and UTIs. Patients were stratified by ML protrusion (<5 mm, 5–10 mm, >10 mm), and postoperative complications and symptom improvements were compared across these categories.
Statistical analysis
Descriptive statistics were used to summarize baseline characteristics by ML protrusion category. Differences in retreatment rates, AUR, and UTI across ML categories were evaluated using chi-square tests or Fisher’s exact test. Changes in IPSSs at follow-up intervals were analyzed using paired t tests or Mann–Whitney U tests, depending on data distribution (parametric or nonparametric). Statistical significance was set at p < 0.05. Since prostate volume and baseline IPSS were comparable across all groups, additional multivariable analysis to adjust for these variables were deemed unnecessary.
Results
Patient characteristics and follow-up
Between July 2020 and September 2023, a total of 208 male patients with BPH underwent WVTT and were included in this analysis. The median follow-up was 29.1 months (range: 24–36 months). Among the study cohort, 113 patients (54%) presented with an ML protrusion, categorized as <5 mm (n = 46, 41%), 5–10 mm (n = 43, 38%), and >10 mm (n = 24, 21%), with the remaining 95 patients (46%) having no ML protrusion. Preoperative characteristics, including age, prostate volume, IPSS, QoL score, and Qmax, were comparable across ML protrusion groups, with no statistically significant differences noted (Table 2).
Comprehensive Longitudinal and Subgroup Outcomes After Water Vapor Thermal Therapy
IPSS = international prostate symptom score; QoL = quality of life; Qmax = maximum urinary flow rate; PVR = postvoid residual volume; SD = standard deviation; UTI = urinary tract infection.
Primary outcomes: Postoperative complications
The incidence of postoperative complications, particularly retreatment rates, varied significantly with the degree of ML protrusion. Overall, 7.7% of patients required retreatment after WVTT, with a notable increase in retreatment among those with greater ML protrusion. Specifically, retreatment was required in 3.2% of patients without ML protrusion, 4.3% with <5 mm protrusion, 14% with 5–10 mm, and 21% in patients with >10 mm ML protrusion (p = 0.007), indicating a statistically significant association between ML size and the likelihood of retreatment (Table 1).
Among the patients who required retreatment, some were managed medically with resumption of BPH medications, whereas others underwent surgical intervention because of persistent lower urinary tract symptoms or inadequate clinical improvement. Surgical retreatments included TURP and other endoscopic procedures, determined at the discretion of the treating urologist.
To determine whether the number of injections correlated with ML size, we analyzed both total injections and ML-targeted injections separately. The mean total number of injections was similar across ML groups (3.44 for patients without ML, 3.48 for <5 mm, 3.15 for 5–10 mm, and 3.21 for >10 mm), with a Kruskal–Wallis test showing no statistically significant difference (p = 0.6244) (Fig. 1). In addition, for injections specifically targeting the ML, there was no significant variation across groups (mean ML injections: 1.38 for patients without ML, 1.50 for <5 mm, 1.40 for 5–10 mm, and 1.35 for >10 mm, p = 0.9046) (Fig. 2). These results indicate that the number of total and ML-specific injections was not significantly influenced by ML protrusion size.
Distribution of total number of injections across median lobe size categories. Box plot showing the distribution of the total number of injections across median lobe size categories (no median lobe, 10 mm). The box represents the interquartile range, with the horizontal line indicating the median. Whiskers extend to 1.5 times the interquartile range, and individual points represent data distribution.
Distribution of injections to the median lobe across median lobe size categories. Box plot showing the number of injections administered to the median lobe across different median lobe size categories (no median lobe, 10 mm). The box represents the interquartile range, with the horizontal line indicating the median. Whiskers extend to 1.5 times the interquartile range, and individual points represent data distribution.
Rates of AUR and UTIs showed no statistically significant differences across the ML protrusion groups. AUR occurred in 9.5% of patients without ML, 8.7% with <5 mm ML, 12% with 5–10 mm, and 17% in those with >10 mm ML (p = 0.7). Among patients who experienced AUR after catheter removal, all were managed conservatively with short-term recatheterization and a repeat voiding trial. Most were able to void effectively after one or two subsequent attempts. No patient required long-term catheterization or emergent intervention.
Similarly, UTIs were observed in 8.4% of patients without ML protrusion, 4.3% with <5 mm, 9.3% with 5–10 mm, and 8.3% with >10 mm protrusion (p = 0.8). These findings suggest that although ML protrusion influences retreatment rates, it does not significantly impact AUR, UTI incidence, or the number of injections administered during the procedure.
Symptom improvement and QoL
Longitudinal changes in IPSS and QoL scores as well as objective measures, including Qmax and PVR at all postoperative follow-up intervals, are summarized in Table 1. Significant postoperative improvements were observed in LUTS across all ML categories, with consistent symptom reduction as indicated by changes in IPSSs. The mean reduction in IPSS from baseline was −13 across all groups, demonstrating substantial symptom relief irrespective of ML protrusion. Both obstructive and irritative components of the IPSS improved, with obstructive scores showing an average reduction of −8.5 and irritative scores decreasing by −4.9, with no statistically significant differences in these changes between ML categories (p > 0.9) (Table 1).
Discussion
WVTT has emerged as an effective treatment for LUTS associated with BPH. Our study demonstrated significant symptom improvement across all degrees of ML protrusion, aligning with previous research indicating substantial reductions in IPSS and enhancements in peak urinary flow rates after WVTT.8,11–14 Our findings indicate that patients with greater ML protrusion experienced higher surgical retreatment rates, an aspect not widely addressed in previous studies. This suggests that although WVTT effectively alleviates LUTS across different ML anatomies, patients with more pronounced ML protrusion may benefit from closer postoperative monitoring or stricter selection criterion based on ML configuration to maintain long-term symptom relief.
Prior studies have suggested that WVTT may be safe and effective in patients with an ML, including those with urinary retention. For example, Bassily and associates reported outcomes in catheter-dependent patients, which differ from our cohort, as we excluded men with retention. 15 Similarly, Elterman and colleagues observed symptomatic improvement in 55% to 65% of patients with an ML. 16 However, this also implies that a substantial proportion—35% to 45%—did not experience significant relief. These findings, along with our own, suggest that although WVTT can be effective in select patients with ML protrusion, it may not be optimal for all. Future studies should aim to identify anatomical or clinical predictors of success, particularly in those with larger or more complex ML configurations.
Understanding the variability of ML anatomy is critical for optimizing patient selection and improving outcomes for WVTT. Preoperative evaluation and categorization of ML IPP into defined groups (<5 mm, 5–10 mm, >10 mm) are essential for guiding individualized treatment strategies. Reliable assessments of ML anatomy, using standardized protocols such as cystoscopy combined with imaging modalities such as TRUS, are essential for identifying patients who may be at higher risk for retreatment. For instance, our study revealed significantly higher retreatment rates in patients with ML protrusion >10 mm, underscoring the need for thorough preoperative counseling to set realistic postoperative expectations. Prior studies, including the pivotal study by McVary and associates and Whiting and colleagues, have shown that the most common reason for retreatment is the undertreatment of ML, emphasizing the significant impact ML anatomy can have on outcomes.7,17 Our findings build on this by suggesting a more nuanced relationship, where the degree of IPP may play a critical role in predicting the durability of WVTT for select patients. By integrating ML anatomy into the decision-making process, clinicians can tailor procedural techniques, recommend closer follow-up, and consider adjunctive interventions for patients with complex ML configurations, ultimately enhancing the safety and durability of WVTT outcomes. Our findings contribute to a growing body of evidence suggesting that ML anatomy—particularly degree of intravesical protrusion—may be a useful factor in guiding patient selection for WVTT.
Although this study has several strengths, including a standardized methodology for evaluating ML anatomy and a robust follow-up period, it does have its limitations. The single-surgeon nature of the study may limit the generalizability of the findings, as outcomes could differ based on operator experience and technique. In addition, although the median follow-up of 29.1 months provides valuable insight into mid-term outcomes, longer term data are necessary to fully understand the durability of WVTT across varying ML anatomies. The relatively small number of patients with >10 mm ML protrusion also limits the statistical power to detect nuanced differences within this subgroup. In addition, although preservation of sexual function is a recognized advantage of WVTT, our study did not formally assess ejaculatory or erectile outcomes using validated instruments such as the IIEF or MSHQ-EjD. This represents a limitation of the present analysis. Future prospective studies should include standardized sexual function assessments to further evaluate the impact of ML anatomy on postprocedure sexual outcomes. Finally, despite using standardized protocols for ML assessment, variability in imaging techniques or operator interpretation may have introduced some bias. Future multicenter studies with larger, more diverse cohorts and longer follow-up are warranted to validate these findings and further refine patient selection and treatment strategies.
Conclusions
WVTT is an effective treatment for LUTS associated with BPH, offering significant symptom relief and the potential to address complex prostatic anatomies, including ML. This study demonstrates that although WVTT provides substantial improvements across varying degrees of ML protrusion, patients with greater IPP are at an increased risk for retreatment. These findings underscore the importance of understanding ML anatomy and its variability in optimizing patient selection and tailoring treatment strategies. Incorporating standardized methods for ML assessment into clinical practice may optimize WVTT outcomes and improve overall patient satisfaction. Further research is needed to validate these findings in larger, more diverse populations and to explore procedural refinements that can address the challenges posed by pronounced ML protrusions.
Authors’ Contributions
J.F.: Conceptualization, methodology, formal analysis, and writing—original draft. J.S.A.: Investigation, data curation, and writing—review and editing. F.L.: Methodology, investigation, visualization, and writing—review and editing. S.A.K.: Supervision, resources, and writing—review and editing. M.P.: Project administration, supervision, and writing—review and editing. C.S.: Formal analysis, data curation, and writing—original draft.
Footnotes
Author Disclosure Statement
No competing financial interests exist.
Funding Information
This research was funded entirely by the Icahn School of Medicine at Mount Sinai and did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.