Radical prostatectomy has historically been the preferred treatment option for patients with localized prostate cancer. However, surgical innovations to reduce blood loss and hasten the recovery rate have led to the introduction of laparoscopic radical prostatectomy (LRP) followed by robot-assisted radical prostatectomy (RARP) as alternatives to open surgery [12]. RARP was introduced to decrease the difficulty in performing complex laparoscopic procedures such as urethral anastomosis. The robotic platform provided several advantages over LRP, such as seven degrees of freedom, tremor filtration, a three-dimensional magnified view, and preferred ergonomics [3]. Therefore, robot-assisted surgery has become popular in Korea, the United States, and Europe [14]. However, this trend has occurred despite a lack of high-quality evidence supporting improvement in outcomes.

Randomized controlled trials comparing the safety and effectiveness of RARP and LRP are limited. Therefore, high-level evidence is a requisite for clinicians needing recent evidence on the treatment of prostate cancer. The primary objective of this study was to determine whether RARP is more effective than LRP in the treatment of prostate cancer in terms of functional, oncological, and perioperative outcomes.

Our study revealed three important findings: (1) the risk of complications after RARP was significantly lower than after LRP; (2) in comparison with LRP, the risk of urinary incontinence at 12 months was significantly lower and the potency rate was higher with RARP; (3) the BCR rate was significantly lower after RARP than after LRP.

The major findings of this meta-analysis showed significant differences in complications such as organ injury and other major complications according to the Clavien-Dindo (III–V) classification. The major complication rate was significantly lower for RARP than for LRP. Although both laparoscopic and robotic surgeries are regarded as minimally invasive techniques, the main advantages of RARP, such as seven degrees of freedom in robotic arm movement and magnified 3D vision of the robotic platform, result in decreased postoperative complications.

Incontinence is another complication of prostatectomy that greatly affects quality of life [5]. The urinary incontinence rate is influenced by the definition of incontinence. Thus, as reported previously, any systematic review is difficult to accomplish owing to the varying definitions used for urinary incontinence, such as involuntary urine loss [6], needing zero or 1 pad [7], and also those in the International Consultation on Incontinence Questionnaire-Short Form survey [8].

The urinary incontinence rate after 12 months was significantly lower with RARP than with LRP in this meta-analysis and in other randomized controlled trials, in which the rates for RARP and LRP were 6% and 17%, respectively, but without statistical significance owing to the limited study population [9]. Many modifications have been suggested in the field of robotics to improve the continence rate. Patel et al. [10] reported a peri-urethral suspension suture technique to improve the rate (92.8% vs. 83%; p=0.013 over 3 months). A modified posterior reconstruction that increased the continence rate by 4 weeks was reported by Coelho et al. [11]. In 2011, Asimakopoulos et al. [9] suggested a pubovesical-complex-sparing technique, in which a ventral plane was developed between the detrusor apron and the prostate. Owing to the technical feasibility of robotic assistance, reconstruction procedures have additionally improved the continence rate.

The potency recovery rate is another major concern for patients undergoing prostatectomy. The most common reason for failure to reach pentafecta is erectile dysfunction (35%) [12]. Our findings differed from those previously reported by NETSCC (2012), which showed no difference in the potency rate between RARP and LRP at 12 months postoperatively. In our meta-analysis, the potency rate of RARP at 12 months was significantly higher than that for LRP. Different potency recovery rates could be due to several factors, including different definitions of erectile dysfunction, various characteristics of the surgery, and differences in postsurgical rehabilitation [13]. Potency recovery was measured by using several methods, including the IIEF-5 and the Sexual Health Inventory for Men score. Various techniques for preserving potency have been developed on the robotic platform, including cavernous nerve preservation. Several nerve-sparing techniques were developed in previous studies. For example, Ahlering et al. [4] evaluated the adverse effects of electrocautery on dissection of the prostate and the superiority of cautery-free nerve-sparing techniques on the recovery of potency. Menon et al. [14] evaluated the “Veil of Aphrodite” technique in which the inter-fascial plane was extended towards the apex and laterally towards the prostatic pedicle. At 6 to 18 months postoperatively, 94% of men who attempted sexual intercourse after undergoing this technique reported success, with a median SHIM score of 18 out of 25. Following recent discoveries of the periprostatic fascial anatomy, extrafascial, interfascial, and intrafascial approaches have been developed. Comparing inter-fascial and extrafascial approaches, Shikanov et al. [15] reported a significantly improved potency rate (p=0.03) using the interfascial approach.

Three-dimensional magnified visualization of the robotic platform has enabled meticulous dissection of the periprostatic fascia layer and the neurovascular bundle. Further insights into the multilayered structure of the periprostatic fascia and the course of the cavernous nerves have supported the development of intra- or interfascial surgical planes, which have enabled improved functional outcomes in urinary incontinence and potency. A PSA level>0.2 ng/mL was selected as the important criterion, based on recommendations of clinical practice guidelines [16]. In an oncological RARP study, Menon et al. [17] reported biochemical-free survival rates of 95.1%, 90.6%, 86.6%, and 81.0% after 1, 3, 5, and 7 years, respectively. Few studies have reported BCR rates after RARP and LRP. Recently, Porpiglia et al. [18] reported BCR-free survival rates of 98% for a RARP group and 92.5% for an LRP group (p=0.190).

The oncologic outcome in the current study was noteworthy because of the statistically signif icant differences in BCR rates between the two groups. Ficarra et al. [13] demonstrated that BCR was significantly influenced by surgical experience, clinical tumor size, and anatomic tumor characteristics. Kim et al. [19] analyzed the preoperative predictors of BCR using multivariable analysis, which suggested that PSA, pathologic stage, pathologic Gleason score, and PSM were independently associated with BCR. In a Japanese study, the predictive factors of BCR following RARP were serum PSA levels, the percentage of positive cores, and the Gleason score. PSA density was also a strong predictor of advanced pathological features and BCR [20]. In our systematic review, the oncologic results for BCR showed a statistically significantly improved BCR in the RARP group relative to the LRP group, although the propensity score matching was similar between the groups. The PSM patients in the intermediate- and high-risk disease groups had higher rates of BCR than did those who were marginal or negative. However, the PSM in the low-risk disease group was not associated with disease progression [21]. After adjustment for differences in clinical and pathological features, the presence of a base margin was significantly associated with a shorter time to recurrence for intermediate- and high-risk disease. The apex margin also was associated with the time to recurrence, but not statistically so for intermediate-risk disease. Thus, the similar PSM rate did not indicate a similar BCR rate. The length of the PSM was also independently predictive of BCR. Patients with a PSM <1 mm appeared to have similar outcomes compared with those with negative surgical margins [22]. Patients with a PSM <1 mm did not differ from those with a negative margin, and as the length of the positive margin increased so did the risk of BCR. Interestingly, the risk of BCR did not differ between patients with a negative surgical margin and those with a PSM <1 mm.

The current study had several limitations. First, because this is a relatively new procedure, data were lacking on long-term oncologic results following RARP, such as the cancer-specific survival rate. Second, significant heterogeneity was evident in terms of surgical experience and definition of functional outcomes. Third, some of recently published articles had far larger cohorts, which strongly influenced the meta-analysis. Fourth, there was an era bias in several centers in that RARP was performed after LRP.

In conclusion, RARP showed favorable results compared with LRP. However, few long-term, high-quality studies are available comparing RARP and LRP. Although further studies are needed, our results revealed that RARP had an improved BCR rate, potency rate, and continence rate with fewer complications than LRP. Further high-quality studies that minimize confounding and selection biases with long-term follow-up are needed to further clarify the clinical efficacy and safety of RARP.