Prostate cancer is the most commonly diagnosed cancer and the second leading cause of cancer-related death in industrialized countries. In Korea, the incidence of prostate cancer is fifth among cancers and is the most rapidly increasing [1]. Radical retropubic prostatectomy (RRP), as described by Walsh [2] in 1982, has been most frequently used to treat localized prostate cancer in the past two decades.

In early 2000, the first robot-assisted laparoscopic radical prostatectomy (RALP) was performed by use of the da Vinci surgical system (Intuitive Surgical Inc., Sunnyvale, CA, USA) in Frankfurt by Binder and Kramer [3]. Through advanced technologies that provide a three-dimensional operative view and laparoscopic instruments that mimic the movement of the human wrist and hand, RALP has reduced the operation time compared with laparoscopic radical prostatectomy.

At present, RRP, the standard treatment modality of localized prostate cancer, has been replaced with RALP because of its minimal invasiveness, reduction in estimated blood loss (EBL), shorter hospital stay, and reduced postoperative pain. However, few comparative studies have evaluated functional outcomes, such as potency and continence, between RRP and RALP. The prevalence of incontinence after radical prostatectomy varies from 2.5% to 87% depending on the definition of urinary control and the evaluation time [4-9].

The purpose of our study was to compare the time until postoperative continence recovery and to evaluate the risk factors for postoperative incontinence in patients who underwent RRP or RALP by a single experienced surgeon.

The mean age of all patients was 65.3±6.4 years, and the mean preoperative prostate-specific antigen concentration was 13.0±20.4 ng/mL. Differences were found between the two patient groups in mean EBL (144.2±204.9 mL vs. 578.1±437.0 mL, p<0.001) and the rate of nerve sparing (56.2% vs. 37.5 %, p=0.004) (Table 1).

Kaplan-Meier curves demonstrated that when continence was defined as a requirement for no pads or a single secure pad per day, the continent rate was significantly higher in group 1 than in group 2 (log-rank test, p=0.008). Also, when continence was defined as no pad use, the continent rate was significantly higher in group 1 than in group 2 (log-rank test, p<0.001). When continence was defined as pad use of 0 to 1 pad per day, 100% of group 1 and 98.2% of group 2 reported continence at 12 months (chi-square test, p=0.189). When continence was defined as no pad use, however, there was a significant difference between the two groups at 12 months: group 1, 95.7%, and group 2, 70.7% (chi-square test, p<0.001) (Fig. 1).

We performed univariate Cox proportional hazard regression analyses to assess for contributing factors to continence recovery. In the univariate analysis, operation method (p<0.001; hazard ratio [HR], 2.493; 95% confidence interval [CI], 1.820 to 3.414), age (p=0.012; HR, 0.971; 95% CI, 0.949 to 0.994), neurovascular bundle saving (bilateral or unilateral: p=0.008; HR, 1.474; 95% CI, 1.108 to 1.961), membranous urethral length (MUL: p=0.009; HR, 2.224; 95% CI, 1.221 to 4.052), EBL (p=0.003; HR, 0.999; 95% CI, 0.999 to 1.000), and apical shape (overlapping vs. nonoverlapping: p=0.025; HR, 1.483; 95% CI, 1.049 to 2.095) were statistically significant. In the multivariate analysis, however, only operation method, age, and MUL retained statistical significance (Table 2).

At present, RRP is considered a standard treatment modality for localized prostate cancer. Despite technological progress, however, some morbidity related to surgery, such as postoperative incontinence, remains and is the same as in the case of minimally invasive surgery. Patient factors such as age, body mass index, and prostate gland volume and surgical factors such as bladder neck-sparing technique, neurovascular bundle preservation, puboprostatic ligament preservation, dorsal vein complex control technique, and maximizing urethral length have been implicated in urinary control after radical prostatectomy but without consistent results.

Since RALP was introduced, Ahlering et al. [14] reported the recovery rates of postoperative incontinence at 3 months for RRP and RALP as 76% vs. 75% (p=not significant), respectively. Di Pierro et al. [15] reported postoperative incontinence recovery at 3 months as 95% for RALP and 83% for RRP (p=0.003) and that after 12 months as 89% for RALP and 80% for RRP (p=0.92). Also, Krambeck et al. [16] reported that there was no significant difference in postoperative continence between RALP (91.8%) and RRP (93.7%) (p=0.344) at 1 year. However, Ficarra et al. [17] reported opposite results of postoperative incontinence for RRP and RALP as 41% vs. 81% after catheter removal (p<0.001) and 88% vs. 97% at 12 months (p=0.01), respectively. Tewari et al. [18] also reported the duration to 50% recovery of postoperative incontinence as 44 days for RALP and 160 days for RRP. These studies used the definition of continence as the use of 0 to 1 pad compared with no pad. But there is no consensus on the definition of continence, and there is movement to standardize the definition of continence as a satisfied, pad-free state. Krupski et al. [5] and Olsson et al. [6] reported that 30% to 55% of patients with no pad use after surgery still intermittently suffer from incontinence. Herein, our study compared the continence state as both no pad and 0 to 1 pad to overcome the problem of previous studies. If the studies by Ahlering et al. [14] and Di Pierro et al. [15] had defined continence strictly as the no pad state, the difference in postoperative incontinence would be intensified.

Paparel et al. [19] reported that MUL before or after surgery has a significant effect on postoperative continence statistically (p<0.01). Those authors reported a close correlation among the amount of MUL loss and postoperative continence (p=0.02) and periurethral fibrosis. Minimizing trauma during the operation to save MUL by correct exfoliation of the prostate apex had an impact on continence [19]. Lee et al. [12] reported a similar result. The results of this study verify that MUL is a significant factor for continence recovery.

In our study, RRP was performed 2 years earlier than RALP. To eliminate selection bias and to minimize the possible learning curve, the RRP group was selected from patients who had undergone RRP just before the 150 consecutive RALP patients.

Our results suggest that advantages for continence recovery may be present in those patients undergoing RALP compared with RRP. The robotic system used in RALP provides a magnified three-dimensional view and precise articulation instruments. These benefits, in terms of urethrovesical anastomosis and anterior reconstruction, might contribute to the early recovery of urinary continence.

The strengths of our study are that the surgery was performed by a single experienced surgeon with uniform surgical technique and we used a validated self-administered questionnaire. To date, some articles have compared oncological and functional outcomes between RALP and RRP, but few comparisons have been made of procedures performed by a single surgeon at a single institute. The comparison that Tewari et al. [18] made in 2003 with 100 cases of RRP and 200 cases of RALP was of procedures performed at a single facility but not by a single surgeon. The comparison that Ficarra et al. [17] made in 2009 between RRP and RALP was also not of procedures performed by a single surgeon. Because a study design with a single surgeon includes the same standards for patient selection and the same postoperative management protocol, such a design has advantages for ruling out the possibility of selection bias and confounding bias.

Our study did have some limitations. First, there was a 2-year gap between the groups for this study. We did not use a quality of life questionnaire for the use of security pads and no pad usage. Finally, the retrospective design may also be a limitation, but we made a concerted effort to complete data collection and minimize bias by designing a prospective database. Therefore, these results should be confirmed by several other surgeons and through well-designed randomized controlled trials. Currently, some randomized controlled trials are in progress, e.g., the laparoscopic prostatectomy robot open study [20].

The results of our study suggest that RALP is an independent factor for the recovery of continence, as were age and MUL, and RALP has advantages for postoperative continence recovery and the quality of continence compared with RRP. This result should be validated by well-conducted prospective randomized controlled trials in the future.