Radical prostatectomy is a commonly used treatment option for patients with clinically localized prostate cancer and a life expectancy of at least 10 years. The most common sequelae of this procedure are urinary incontinence and erectile dysfunction, which significantly affect patients’ quality of life and result in both physical and psychosocial burdens. Robot-assisted radical prostatectomy (RARP) has become widely used worldwide, and RARP has been shown to have lower postoperative urinary incontinence rates than retropubic or laparoscopic radical prostatectomy in a recent systematic review and meta-analysis [1]. Several groups have reported that the nerve-sparing (NS) procedure contributes not only to the recovery of erectile function, but also to the improvement of urinary incontinence [2]. However, the underlying mechanism of the impact of the NS procedure on lower urinary incontinence remains unclear. Moreover, there is a relative paucity of data on the impact of the NS procedure on lower urinary tract symptoms (LUTS) with the exception of urinary incontinence, especially in the context of RARP. The aim of this study was to investigate the impact of the NS procedure on LUTS, including urinary incontinence, after RARP.

The study protocol was approved by the institutional ethics committee for clinical trials. The participants in this prospective, clinical cohort, observational study were 280 consecutive patients who underwent RARP at our institution between October 2010 and January 2016. All patients were urinary continent before surgery. All patients admitted to the hospital scheduled for RARP were asked to join a prospective data collection protocol. All patients signed an institutional ethical committee-approved informed consent form, and all patients were informed that data would be used anonymously for the purpose of clinical research. On acceptance, preoperative data were prospectively collected for each participant. Data analyses for the purpose of the present study were performed retrospectively. All prostatectomies were performed via the 6 port transperitoneal approach. Surgical procedures were performed by three different surgeons. NS techniques were performed using a similar method according to the four grades of posterolateral resection of the prostate: grade 1, intrafascial dissection; grade 2, interfascial dissection; grade 3, extrafascial dissection; grade 4, wide dissection. In this study, NS was defined as NS grade 1 or 2 and non-NS was defined as NS grade 3 or 4. The International Prostate Symptom Score (IPSS), IPSS subscore including voiding and storage, The Overactive Bladder Symptom Score (OABSS), and urinary incontinence were assessed preoperatively (2 days before RARP) and at 1, 3, 6, 9, and 12 months after RARP. All patients completed preoperative questionnaires on admission for RARP and were mailed follow-up questionnaires at 1, 3, 6, 9, and 12 months after RARP. Postoperative urinary incontinence was assessed at scheduled visits 1, 3, 6, 9, and 12 months after RARP. The IPSS voiding subscore has been defined as the sum of the scores for questions 1, 3, 5, and 6, and the storage subscore has been defined as the sum of the scores for questions 2, 4, and 7. Patients who used no pads were considered to be urinary continent and those who used one or more security liner pads per day were considered to be urinary incontinent. To investigate the effects of the NS procedure on LUTS, the patients were divided into two groups (the bilateral or unilateral NS group and non-NS group). Between-group differences in the IPSS total score, the IPSS voiding subscore, the IPSS storage subscore, and OABSS total score at different time-points were calculated using the unpaired samples t test. Between-group differences in changes from baseline to 1, 3, 6, 9, and 12 months were evaluated by analysis of variance (ANOVA). Kaplan-Meier curve estimates were used to assess urinary incontinence rates in each group at 1, 3, 6, 9, and 12 months after RARP. All statistical tests were two sided with a significance level set at P < 0.05. According to power calculation, a sample size of 118 patients per group was needed.

The distribution of NS type was bilateral NS, unilateral NS and non-NS in 6.4% (n = 18), 36.8% (n = 103), and 56.8% (n = 159) of patients, respectively. Urinary continence rates at 1, 3, 6, 9, and 12 months after RARP were 33.5%, 51.5%, 67.8%, 79.1%, and 84.7%, respectively. There were significant differences in the recovery of urinary continence after RARP (log-rank test, P = 0.01): 12 month post-operative urinary incontinence rates were 14.3% (bilateral or unilateral NS group) and, 27.5% (non-NS group). All patients showed increases in the IPSS total score at 1 month but then improved back to baseline level at 3 months. At 6, 9, and 12 months, the IPSS total scores were significantly lower than those at baseline. At 3 months, the IPSS voiding subscore improved by approximately 30% compared to baseline and remained stable over the long term. All patients experienced an 84% increase at 1 month in the IPSS storage subscore, but then improved back to baseline level at 6 months and remained stable over time. No differences in the IPSS total scores, the IPSS voiding subscores, the IPSS storage subscores, and OABSS total scores at 1, 3, 6, 9, and 12 months were identified between the bilateral or unilateral NS group and non-NS group.

The present study investigated the associations between the NS procedure and LUTS after RARP. The results of this study indicated that the NS procedure could achieve early improvement of urinary incontinence, although the NS procedure did not affect improvement of LUTS, with the exception of urinary incontinence, after RARP. A recent review showed that when performing non-NS surgeries, both somatic and autonomic nerves are at risk of damage, due to either wide excision at the level of the seminal vesicles or the peri-prostatic dissection, or at the level of the apex where convergence occurs and the nerves are within a few millimeters of the dissection plane and suture bites [3]. The somatic and autonomic nerves travel within the layers of the fascia of the levator ani and could sustain injury if the resection plane is sufficiently wide. Therefore, the NS procedure may lead to early improvement of urinary incontinence after RARP. There are several limitations of this study. First, it was an observational study with retrospective analysis of prospectively collected data. Second, urodynamic studies were not analyzed. Abnormal findings of urodynamic studies do not always coincide with a patient’s subjective symptoms, even though several investigations have analyzed the correlation between radical prostatectomy and urodynamic bladder dysfunction. Third, the present study could not investigate the impact of the bilateral NS procedure on LUTS after RARP, because the sample size of the bilateral NS group was too small. Finally, our cohort represents data from a single institution. Additionally, our cohort might not be sufficiently large enough to show small differences in outcomes. Further testing will be required to determine whether our findings are applicable to other cohorts.

The NS procedure in RARP has the possibility to improve urinary incontinence after surgery, although the NS procedure in RARP did not ameliorate LUTS, with the exception of urinary incontinence. Therefore, if possible, the NS procedure is recommended from the viewpoint of early improvement of urinary incontinence after RARP.

Ficarra V, Novara G, Rosen RC et al. Systematic review and meta-analysis of studies reporting urinary incontinence recovery after robot-assisted radical prostatectomy. Eur Urol 2012; 62:405-417.
Steineck G, Bjartell A, Hugosson J et al. Degree of preservation of the neurovascular bundles during radical prostatectomy and urinary continence 1 year after surgery. Eur Urol 2015; 67:559-568.
Bessede T, Sooriakumaran P, Takenaka A et al. Neural supply of the male urethral sphincter: comprehensive anatomical review and implications for continence recovery after radical prostatectomy. World J Urol 2017; 35:549-565.