Authors (including presenting author) :
Brian W.H. Siu(1), Alex Q. Liu(1), Chi Ho Leung(1), Steffi K.K. Yuen(1), David K.W. Leung(1), Chris H.M. Wong(1), Ivan C.H. Ko(1), Ryan W.Y. Yuen(1), Henry Y.H. Meng(1), Jeremy M.H. Ho(1), Chi Hang Yee(1), Jeremy Y.C. Teoh(1), Irene Wu(1), Hilda Kwok(1),Chi Fai Ng(1), Peter K.F. Chiu(1) and Ka Lun Lo(1)
Affiliation :
(1) SH Ho Urology Centre, Department of Surgery, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, China.
Introduction :
Benign prostatic hyperplasia (BPH) and its associated complications, particularly acute urinary retention, pose a significant social and economic burden on healthcare systems worldwide. While transurethral resection of the prostate (TURP) remains the surgical gold standard for refractory retention due to BPH, requirement of general or spinal anesthesia limits its applicability in certain patient populations. In recent years, minimally invasive surgical therapies (MIST) for BPH have emerged as viable alternatives that can be performed under local anesthesia in ambulatory settings.
The Rezūm system (Boston Scientific Company Inc., Marlborough, MA, USA), which is transurethral water vapor thermal therapy, has shown promise as a MIST for treating lower urinary tract symptoms (LUTS) secondary to BPH. As an office-based operation under local anesthesia, it offers a potential solution for patients who are poor candidates for more invasive procedures. This advantage had become particularly relevant in the context of the COVID-19 pandemic, which had severely impacted services for operations requiring general or spinal anesthesia in our locality, especially for benign conditions.
Conventionally, the number of water vapor treatment cycles in Rezūm procedures has been determined by the prostate length or the fields of vision (FOV), as recommended by the manufacturer. While this approach has shown efficacy in treating BPH-related lower urinary tract symptoms (LUTS), its applicability to patients with catheter-dependent refractory retention remains uncertain. Owing to the variations of shape in prostate lobes, it is conceivable that the universal adoption of a FOV-based approach may undertreat some BPH patients, which potentially leads to suboptimal improvement of symptom and uroflowmetry outcomes.
In this study, we introduce a novel concept: Treatment Cycles Per Unit Prostate Volume (CPV). This metric enables an objective determination of the ‘density’ of water vapor treatment cycles according to individual prostate sizes, analogous to the concept of prostate-specific antigen density in prostate cancer diagnosis. We hypothesize that a higher CPV may lead to better and more durable voiding improvement.
Objectives :
To explore the impact of CPV on safety and efficacy among catheter-dependent patients.
Methodology :
The inclusion criteria were male adults suffering from refractory urinary retention due to BPH, who had failed at least one trial without catheter (TWOC) after the addition of an alpha blocker. Exclusion criteria included prior prostate surgery, known history or strong clinical suspicion of prostate cancer, and known urinary tract functional or structural abnormalities such as urethral stricture and neurogenic bladder. After the urologist’s assessment for eligibility and obtaining informed consent, patients were assessed with a standard preoperative assessment, including demographic data collection, uroflowmetry, and prostate size measurement by transrectal ultrasonography, etc. Then, the procedure would be performed accordingly with perioperative parameters collected. Postoperatively, the patient would be followed according to our standardized protocol, including (1) A nurse led phone consultation scheduled at post op six weeks, enquiring on symptoms, complications (e.g. hematuria, dysuria, incontinence) and voiding symptom score (e.g. IPSS, OABSS overactive bladder symptoms score); (2) A physical follow up at post op three months, include, questionnaires assessment, uroflowmetry and PSA testing; (3) A follow up visit at one year after surgery. The Rezūm procedure was performed under local anesthesia via periprostatic block, as previously described in the literature [4, 5, 6]. CPV (Treatment Cycles Per Unit Prostate Volume) was calculated by dividing the number of treatment cycles by the preoperative prostate size. The primary outcome was IPSS at 1 year. Secondary outcomes included time to successful TWOC, 30 day readmission rates, prostate size and PSA reduction. To reduce confounding effects, we performed propensity score matching with age and baseline prostate size as covariates, using a 1:1 optimal pair matching approach. The balance between groups was assessed before and after matching, with an absolute standardized difference of < 0.1 indicating good balance. The baseline characteristics of the higher and lower CPV group were compared using the Student’s t test. We used logistic regression models with cluster robust standard errors to estimate the average marginal effect of higher CPV on 30 day TWOC rate, readmission rate, and culture positive UTI rate. Median time to successful TWOC was analyzed using the Mann Whitney U test. Linear mixed models were employed to compare IPSS, Qmax (maximal flow rate), and PVR (post void residual urine volume) between higher and lower CPV groups over time. These models included treatment group, follow up visit, and their interaction as fixed effects, with random intercepts to account for patient-specific heterogeneities.
Result & Outcome :
From 2021 to 2023, 168 men with catheter dependent refractory retention underwent Rezūm, with 96 in the CPV ≤ 0.15 group and 72 in the CPV > 0.15 group. After propensity score matching, 72 patients were selected from each group for analysis with ASD (absolute standardized difference) values of 0.038 for age and 0.089 for prostate size, indicating good balance between the groups.
The CPV > 0.15 group demonstrated significantly lower IPSS at 1 year (adjusted mean difference 2.8, 95% CI 5.5 to 0.1, p = 0.040). The IPSS at 3 months were similar between the two groups (p = 0.864). The CPV > 0.15 group also showed significantly greater PSA drop at three months (log transformed PSA reduction adjusted mean difference 0.4 ng/ml, p=0.022). With balanced preoperative prostate size, the advantage of CPV > 0.15 group in prostate size reduction did not reach statistical significance at 3 months (adjusted mean difference 1.8 ml, 95% CI 5.3 to 1.6, p = 0.299). There were no significant differences in Qmax and PVR between the two groups (p = 0.120 and p = 0.181, respectively).
There was no statistical difference between 30 day successful trial without catheter (TWOC) rates of CPV ≤ 0.15 group (75.0%) and the CPV > 0.15 group (68.1%) (OR 0.71, 95% CI 0.33 1.51, p = 0.372). Median durations to successful TWOC were 14 days (IQR: 9 – 29 days) and 15 days (IQR: 12 – 40 days) for CPV ≤ 0.15 group and CPV > 0.15 group respectively (p = 0.059). The 30 day readmission rate was significantly lower in the CPV > 0.15 group (4.2%) compared to the CPV ≤ 0.15 group (16.7%) (OR 0.22, 95% CI 0.06 0.86, p = 0.029). Among all readmissions, recurrent urinary retention was the most common cause (53.3%) of all readmissions. Notably, patients who experienced recurrent retention mostly (75%) belong to the CPV ≤ 0.15 group, with only two cases (25%) occurring in the CPV >0.15 group.
In summary higher CPV in Rezūm improved 1 year IPSS and lowered 30 day readmission rates in our matched cohort. A more aggressive treatment approach using higher CPV may be beneficial for catheter dependent patients with refractory urinary retention. Further prospective studies with larger sample sizes, are warranted to validate these results and establish optimal CPV thresholds for different patient populations.
