Predictors of prolonged severe urinary incontinence after robot-assisted radical prostatectomy: a prospective study

Abstract

Objectives:To identify predictors of prolonged severe urinary incontinence after robot-assisted radical prostatectomy (RARP), perioperative clinical parameters were investigated.

Methods:Participants were 299 patients who underwent RARP at our institute.　Prolonged severe urinary incontinence was defined as a 1-h (one-hour) pad test >50 g/h and/or use of >3 pads/day at 12 months after RARP.　The cohort was divided into severe and non-severe urinary incontinence groups according to this criterion.　Perioperative clinical parameters were compared between groups to identify predictors for prolonged severe urinary incontinence after RARP.

Results:Twenty-seven patients (9.0%) were categorized into the severe urinary incontinence group.　The remaining 272 patients (91.0%) were categorized into the non-severe urinary incontinence group.　Univariate analysis revealed prolonged severe urinary incontinence as significantly associated with older age (P=0.011), high BMI (P=0.001), lymph node dissection (P=0.003), non-preservation of nerves (P=0.039), non-preservation of fascia of the levator ani muscle (P=0.009), and high risk in the D’Amico risk classification (P=0.010).　Multivariate analysis revealed prolonged severe urinary incontinence as significantly correlated with high BMI (P=0.009) and high risk in the D’Amico risk classification (P=0.007).

Conclusions:High BMI and D’Amico high-risk status are associated with prolonged severe urinary incontinence after RARP.

Introduction

Robot-assisted radical prostatectomy (RARP) for patients with localized prostate cancer has gained wide acceptance all over the world, and procedures for maintaining urinary continence have been improving since the introduction of RARP¹⁾.　RARP is well known to show good outcomes regarding postoperative urinary continence compared with conventional radical prostatectomy²⁾.　Although many patients have experienced urinary incontinence just after RARP, Ficarra et al. reported that 84-97% of those patients achieved urinary continence by 12 months after RARP, because urinary incontinence often shows gradual improvement over time²⁾.　 However, some patients who underwent RARP suffered from prolonged and severe urinary incontinence after RARP^3-7).　These patients experienced interference with quality of life^3,4), and sometimes needed additional operations to ameliorate post-prostatectomy urinary incontinence^5-7).　Even in the RARP era, 3.6% of patients underwent subsequent incontinence surgery, such as urethral sling or artificial urinary sphincter placement⁷⁾.

Although prolonged severe urinary incontinence is a particularly important problem for patients after RARP, its frequency and predictors have yet to be fully elucidated.　At our institute, differences among surgeons reconstructing the lower urinary tract were minimal, thanks to supervised, meticulous maneuvering, guided by 3-dimensional and magnified clear vision during RARP.　Thus, we hypothesized that perioperative clinical parameters, including preoperative patient status, might affect the severity of post-prostatectomy incontinence.　In this study, relationships between prolonged severe urinary incontinence and perioperative clinical parameters were evaluated to identify predictors of prolonged severe urinary incontinence after RARP.

Materials and Methods

Patients

This prospective study was open to 334 consecutive patients who underwent RARP for clinically localized prostate cancer at our institution between February 2013 and August 2022.　Both a 1-h (one-hour) pad test and the number of pads used in a day were prospectively assessed at 1, 3, 6, 9 and 12 months after RARP to evaluate urinary incontinence.　Among these 334 patients, 35 patients were excluded for incomplete compliance with study protocols:23 could not be followed-up for 12 months after RARP, and in 12 others either the 1-h pad test or number of pads used were not assessed at 12 months after RARP).　Informed consent was obtained from all patients before enrolment in the study.　All study protocols were approved (#2334) by our institutional review board, which is guided by local policy, national law, and the World Medical Association Declaration of Helsinki.

Operative procedures

All patients underwent RARP using a 4-arm Da Vinci Si surgical system (Intuitive Surgical, Sunnyvale, CA).　Combining posterior and anterior intraperitoneal approaches, the seminal vesicles and vasa deferentia were exposed at an early stage during RARP⁸⁾.　For posterior reconstruction, the Rocco technique was performed⁹⁾, and some patients underwent a three-layer two-step posterior reconstruction using peritoneum¹⁰⁾.　The nerve-sparing procedure and/or preservation of fascia of the levator ani muscle were performed only for those patients who showed low or intermediate risk according to the D’Amico risk classification.　All operations were performed under the guidance of an experienced supervisor (YK).

Evaluation of urinary incontinence

Several studies have reported the 1-h pad test and pad count as objective measures of the severity of urinary incontinence^5,11,12).　This study therefore assessed both the 1-h pad test and pad counts at 1, 3, 6, 9 and 12 months after RARP.　The 1-h pad test was performed according to International Continence Society recommendations¹¹⁾.　Prolonged severe urinary incontinence was defined by >50 g from the 1-h pad test and/or use of >3 pads/day at 12 months after RARP.　Patients were divided into severe and non-severe urinary incontinence groups.　The non-severe urinary incontinence group included patients with urinary continence after RARP (Figure 1).

Relationships between prolonged severe urinary incontinence and perioperative clinical parameters

To identify predictors of prolonged severe urinary incontinence after RARP, the severe and non-severe urinary incontinence groups were compared in regard to preoperative patient status and perioperative parameters.　Age, body mass index (BMI), prostate-specific antigen (PSA), D’Amico risk classification, and Charlson comorbidity index (CCI) were assessed preoperatively, because reports have implicated these factors in urinary incontinence after radical prostatectomy^13-21).　CCI is a predictor of patient survival, as an index comprising the sum of scores for comorbidities²²⁾.　Perioperative parameters included surgical time, estimated blood loss, weight of excised prostate, lymph node dissection, posterior reconstruction, preservation of nerves, preservation of fascia of the levator ani muscle and pathological tumor classification (pT classification).

Statistical analysis

All values are expressed as mean ± standard deviation.　Between the severe and non-severe urinary incontinence groups, univariate analysis was performed to screen statistically significant variables for inclusion in further multivariate analysis.　The Mann-Whitney U-test or chi-square test were used for univariate analyses.　Logistic regression analysis was employed for multivariate analysis.　Values of P<0.05 were considered statistically significant.　Analyses were performed with IBM SPSS Statistics version 24.0 software (Statistical Package for Social Sciences, Chicago, IL).

Fig. 1.

Definition of severe and non-severe urinary incontinence groups and exclusion criteria

“Prolonged severe” urinary incontinence was based on the 1-h pad test and number of pads used in a day at 12 months after RARP, after which patients were divided into severe and non-severe urinary incontinence groups.

Results

Preoperative patient status and perioperative parameters of 299 patients who underwent RARP are shown in Table 1.　Among the 299 patients who completed the study, 27 patients (9.0%) were categorized in the severe urinary incontinence group, and the remaining 272 patients (91.0%) were allocated to the non-severe urinary incontinence group (Figure 1).　Mean volumes for the 1-h pad test in each group were 65.7 ± 68.3 g and 2.4 ± 5.2 g at 12 months after RARP, respectively (P<0.001).　Mean numbers of pads used daily in each group were 2.7 ± 0.5 and 0.5 ± 0.6 at 12 months after RARP, respectively (P<0.001) (Table 2, Figure 2).

Table 3 shows the comparison of patient characteristics and perioperative outcomes between the severe and non-severe urinary incontinence groups.　Age (P=0.011) and BMI (P=0.001) were significantly higher in the severe urinary incontinence group.　Significantly more patients with severe urinary incontinence belonged to the D’Amico high-risk group (P=0.010).　The percentage of patients who underwent nerve-sparing (P=0.039), preservation of the fascia of the levator ani muscle (P=0.017), or who did not undergo lymph node dissection (P=0.003) were significantly higher in the non-severe urinary incontinence group than in the severe urinary incontinence group.　No significant differences in PSA, CCI, surgical time, estimated blood loss, weight of excised prostate, posterior reconstruction, or pT classification were evident between the severe and non-severe urinary incontinence groups.　Multivariate analysis was performed using these six factors as independent variables.　 Prolonged severe urinary incontinence correlated significantly with high BMI (P=0.009) and high risk in the D’Amico risk classification (P=0.007) (Table 4).

We attempted to identify the optimal cut-off for BMI to predict prolonged severe urinary incontinence.　Figure 3 shows the receiver operating characteristic (ROC) curve for BMI, which suggested a cut-off BMI of 25.3 kg/m², offering 74.1% sensitivity and 70.6% specificity.

Table 1.

Preoperative patient status and perioperative parameters

Results are given as the number or mean ± standard deviation or ratio (number).

Table 2.

Categorization of severity of urinary incontinence at 12 months postoperatively

Results are given as number or mean ± standard deviation (range).　Values of P<0.05 were considered statistically significant.

Fig. 2.

Mean volume in 1-h pad test and mean number of pads used daily in non-severe and severe urinary incontinence groups

A) Mean volume in 1-h pad test

B) Mean number of pads used daily

Values of P<0.05 were considered significant.

Table 3.

Univariate analysis (Mann-Whitney U-test) of parameters for the non-severe and severe urinary incontinence groups

Results are given as the number or mean ± standard deviation or ratio (number).　Values of P<0.05 were considered statistically significant.

Table 4.

Multivariate analysis (logistic regression analysis) to identify factors affecting prolonged severe urinary incontinence

Values of P<0.05 were considered statistically significant.

Fig. 3.

Receiver operating characteristic (ROC) curve for using BMI to predict prolonged severe urinary incontinence

Arrow indicates optimal cut-off for use of BMI to predict prolonged severe urinary incontinence.

Discussion

Even with RARP as a well-established procedure, postoperative urinary incontinence persists as a significant adverse outcome of radical prostatectomy^3,4).　Ficarra et al. showed that the recovery rate of urinary continence at 12 months after RARP ranged from 84% to 97%, and RARP showed a significant advantage in the recovery of urinary continence compared with retropubic radical prostatectomy (RRP) and laparoscopic radical prostatectomy (LRP)²⁾.　Although many studies have reported factors involved in urinary continence after RARP^13-20,23-25), results have differed from study to study and remain controversial.　No previous studies appear to have focused on “prolonged” and “severe” urinary incontinence, both of which represent an extreme impingement on quality of life.　In this study, we evaluated urinary incontinence at 12 months postoperatively to investigate “persistent” urinary incontinence.　Additionally, to focus on “severe” urinary incontinence, we included patients with mild to moderate urinary incontinence in the control group.　This is the first research to associate high BMI and high risk in the D’Amico risk classification with prolonged severe urinary incontinence after RARP.

Other reports have described age, BMI, CCI, prostate volume, and preoperative lower urinary tract symptoms (LUTS) as factors affecting urinary incontinence after RARP^13-20).　Our study, focusing on prolonged severe urinary incontinence, also revealed high BMI as significantly associated with prolonged severe urinary incontinence.　Ahlering et al. reported that, at 6 months after RARP, the rate of achieving pad-free status among patients with excess body weight (BMI ≥30 kg/m²) was only 47%, compared to 91.4% among non-obese patients (P≤0.001)¹³⁾.　Wiltz et al. reported that urinary continence outcomes after RARP were significantly lower for obese men at both 12 and 24 months in their cohort stratified by BMI¹⁴⁾.

Apart from post-prostatectomy urinary incontinence, some studies have linked obesity to urinary incontinence in general, and concluded that obese individuals are at greater risk of this symptom^26-28).　The underlying mechanisms are not completely understood, but some reports have noted that among obese patients with metabolic syndrome, adipose tissue excessively releases adipocytokines that provoke LUTS as a consequence of inflammation or oxidative stress^26,27).　Ryu et al. also reported that wound healing in obese patients was delayed because adiponectins, which promote wound healing, were decreased in their adipose tissue²⁸⁾.　Thus, among obese patients, more adipocytokines or reduced adiponectins might impede recovery of pelvic floor function, prolonging urinary incontinence.

As another mechanism inducing prolonged severe urinary incontinence after RARP in obese patients, Hunskaar et al. reported that for obese woman, excess body weight increased abdominal pressure, in turn increasing bladder pressure and urethral mobility²⁹⁾.　As a result, urinary incontinence frequently arises in obese woman.　The anatomical structures in males after RARP resemble those of normal females due to the removal of the prostate³⁰⁾.　The increased bladder pressure resulting from obesity thus might also increase urinary incontinence after RARP.　Weight reduction may improve urinary continence after RARP.

The present study also revealed that high risk according to the D’Amico risk classification is significantly associated with prolonged severe urinary incontinence.　In patients with high risk in the D’Amico classification, extended resection is often performed to achieve radical cure, resulting in no preservation of nerves, proximal urethra, bladder neck, fascia of the levator ani muscle, or Denonvilliers’ fascia, all of which are considered to contribute to the maintenance of urinary continence³⁰⁾.　Extended resection is likely to cause more severe damage to the pelvic floor, and this would not improve even with time, leading to prolonged severe urinary incontinence.

In the present study, high BMI (>25.3 kg/m²) and high-risk D’Amico risk classification were identified as potential predictors of prolonged severe urinary incontinence after RARP.　This finding, conveyed preoperatively to patients, would enhance the process of informed consent prior to RARP.

Several methodological limitations must be considered when interpreting the results of the present study.　This study enrolled a small sample size from only a single institution.　No assessments of preservation of the urethra or bladder neck were performed.　These factors might influence urinary incontinence.　We welcome the prospect of a larger multicenter study including a wider array of factors that may affect or predict quality of life after RARP.

Conflict of Interest Disclosure

The authors have no conflict of interest to disclose.

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