While robot-assisted radical prostatectomy (RARP) is a safe operation even for aged male patients with localized prostate cancer (PCa), urinary functional outcomes after RARP critically influence their quality of life. Regarding the predictive factors of early or intermediate-term continence following RARP, some aspects including age, obesity, postoperative membranous urethral length, surgical procedures and prostate volume, have been reported (1-3). However, urodynamic study (UDS) parameters associated with a prediction of continence after RARP remain unclear. In this study, we investigated the relationship between UDS data and recovery of urinary incontinence of elder patients who underwent RARP.

Between April 2014 and December 2017, seventy-five PCa patients received UDS before and at 3 months after RARP performed by one surgeon (TT) at our institution. The surgical technique was performed as previously reported by Menon et al. UDS contained pressure flow studies and urethral pressure profiles. We divided them into two groups; young group (less than 70 years old, n=47) and senior group (70 years old and over, n=28), and then classified each group as urinary continence (UC) or incontinence (UI) in the assessment of urinary function at post-RARP 3 months. Continence was defined by 0-pad or 1-safety pad usage at 3, 6 months follow-up. Patient and operative characteristics included body mass index (BMI), initial prostate-specific antigen (iPSA), staging, prostate volume, operation time, blood loss volume and performance of nerve sparing. Statistical analyses were performed with the software package SPSS. All tests were two-sided, with a statistical significance set at p < 0.05. Categorical distributions were reported as counts (%) and continuous variables as medians and interquartile range. The Chi-square test was used to assess differences in distributions among categorical variables. The Mann–Whitney U test was used to assess the difference in distributions among continuous variables. Univariable and multivariable logistic regression models were constructed to assess for predictors of continence 6 months following surgery.

There is no significant difference in continence rate at 3 months after RARP between the young and senior group (68.1 % vs 64.3 %, p= 0.67). In the senior group, the preoperative maximum urethral closure pressure (MUCP) of UI was significantly lower than that of UC (71.1± 40 vs 112.8± 50.7, p= 0.039), and there is no significant difference between preoperative functional length of the urethra (FLU) of UI and that of UC. The presence rate of detrusor overactivity (DO) of UI was significantly higher than that of UC in the senior group at both pre- and post-RARP 3 months, respectively (pre-RARP: 60% vs 33.3%, p<0.05; post-RARP: 80% vs 33.3%, p= 0.001). Other variables (BMI, iPSA, staging, prostate volume, operation time, blood loss volume and nerve sparing) did not differentiate significantly between UC and UI in the senior group. The rate of de novo DO at postoperative 3 months in the senior group was significantly low compared with that in the young group (p<0.001). Moreover, multivariate regression analysis in total patients revealed that the postoperative DO was an independent predictor of incontinence at 6 months following RARP (odds ratio [OR] 5.0, confidence interval [CI] 95%: 1.4, 18.6).

In elder patients, low MUCP and DO before RARP may be a potential risk of the delayed recovery of postoperative UI. In particular, most of elder patients with the preoperative DO had the postoperative DO. 
The presence of DO after RARP may greatly contribute to the persistent UI regardless age.

In elder PCa patients, active interventions such as pelvic floor muscle training with biofeedback and pharmaceutical treatment of overactive bladder may be needed for early recovery of UI after RARP.

Yamada Y, Fujimura T, Fukuhara H et al. Overactive bladder is a negative predictor of achieving continence after robot-assisted radical prostatectomy. Int J Urol. 2017; 24: 749-56.
Bartoletti R, Mogorovich A, Francesca F, Pomara G, Selli C. Combined bladder neck preservation and posterior musculofascial reconstruction during robotic assisted radical prostatectomy: effects on early and long term urinary continence recovery. BMC Urol. 2017; 17: 119.
Song W, Kim CK, Park BK et al. Impact of preoperative and postoperative membranous urethral length measured by 3 Tesla magnetic resonance imaging on urinary continence recovery after robotic-assisted radical prostatectomy. Can Urol Assoc J. 2017; 11: E93-E9.