The Posterior Surgical Approach to Robot-Assisted Radical Prostatectomy Facilitates Dissection of Large Glands

Introduction

R adical retropubic prostatectomy remains the gold standard approach to surgery for clinically localized prostate cancer. An evolution of minimally invasive surgery using laparoscopic and, more recently, robotic equipment, however, has occurred with the first laparoscopic radical prostatectomy described in 1992. ¹ Widespread adoption of pure laparoscopic prostatectomy has been slow given the steep learning curve associated with the procedure. With the advantages of a robot-assisted laparoscopic approach, including magnified stereoscopic vision, intuitive movements, seven degrees of freedom, and motion scaling, the learning curve is less severe and allows for a more universal adoption of a minimally invasive radical prostatectomy.

Important with all surgery is the critical review of the procedure and constant modification to improve outcomes based on the results. That said, although the laparoscopic prostatectomy (LP) and robot-assisted radical prostatectomy (RARP) differ in some technical aspects, the overall surgical principles and oncologic and functional goals are the same for the two different approaches. RARP affords two potential approaches to dissection of the seminal vesicles: The anterior approach was described first by Menon and associates ² at the Vattikuti Urology Institute while the posterior approach was adapted from the Montsouris technique of LP. ³ To our knowledge, there have been no comparisons in the urologic literature to suggest superiority of one approach over the other.

Patients and Methods

Since the inception of a robotics program, an Institutional Review Board-approved prospective database of all RARPs performed at our institution has been maintained by an independent third party. We sought to compare our experience between an anterior and posterior approach to robot-assisted prostatectomy. The surgical approach is based on surgeon preference, and during the study period between 2007 and 2011, 404 patients undergoing RARP were reviewed.

Of the 404 patients, 187 patients underwent RARP via a posterior surgical approach by one surgeon while 217 patients were approached anteriorly by a second surgeon. It is noteworthy that both of the surgeons included in this review were robotic-naïve at the onset of the study. Retrospective review of preoperative, intraoperative, and perioperative characteristics and outcomes were compared between the two cohorts with Microsoft Excel 2001 (1985–2001 Microsoft Corporation, Redmond, WA) using two sample t tests and two proportion z tests to calculate statistical significance.

Given the potential of prostate anatomy to affect outcomes differently between the two approaches, the cohort was divided into quartiles to assess the effect of prostate volume on surgical outcome. Quartiles were determined based on descriptive statistical principles such that each quartile represents 25% of the entire population. Prostate volumes were assessed by ultrasound measurements at the time of transrectal prostate biopsy because this would be information available to guide preoperative decision-making as opposed to surgical weight. Those patients for whom prostate volume was not available preoperatively were excluded from the quartile analysis.

Results

There were no significant differences in age, body mass index, prostate volume, or prostate-specific antigen between the two cohorts. Pathology was similar, although there was a significantly increased proportion of Gleason 9 disease in the anterior approach group as seen in Table 1.

Intraoperative and perioperative outcomes including console time, transfusion rate, positive margins, and complication rates were compared. The 30-day perioperative complications were recorded by an independent third party and included any aberration from our previously defined ideal perioperative course. ⁴

There was no difference observed in outcomes or console time between the two approaches (Table 2). We then analyzed the two groups based on prostate volume quartiles to investigate the effect of prostate size on efficiency of the surgical approach. Prostate quartiles were 13–29 cc, 29–35 cc, 35–50 cc, and >50 cc. In the posterior approach cohort, there were 46, 48, 48, and 42 patients in the first to fourth quartile, respectively, while the anterior approach consisted of 46, 44, 42, and 49 patients, respectively. When console time was stratified for prostate volume, a shorter operative time was seen in the two highest quartiles for prostate volume with the posterior approach (163.8 vs 145.9 min and 183.8 vs 166.2 min, P=0.02, P=0.04) as seen in Figure 1.

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FIG. 1.

Console time by prostate volume.

To ensure this advantage with the posterior approach was not a result of discrepant prostate volumes along the early learning curve, we compared the proportion of patients in the four quartiles within each surgeon's first 100 patients. There were no differences in the proportion of patients within the quartiles for each approach in the first 100 patients (data not shown, P>0.05).

Discussion

RARP has lowered the learning curve and increased the applicability of minimally invasive surgery in the treatment of patients with prostate cancer. In 2008. 75% to 85% of radical prostatectomies were performed with robotic assistance in the United States. ^5,6 Despite its prevalence as a treatment entity, to our knowledge, there has been no comparison in the literature with regard to divergent approaches to the seminal vesicle (SV) dissection.

Although one of the most prolific robotic centers agrees on the importance of “the window” sign (the connection of the anteriorly and posteriorly dissected planes in the retrovesical/retroprostatic space), there appears to be two different means to achieve this window. ⁷

Supporters of a posterior approach during RARP suggest that direct access to the SVs is easily achieved regardless of the size of the patient, the shape and size of the prostate, or the presence of a median lobe. In addition, the posterior approach may eliminate working in a narrow hole, an obstacle potentially encountered during the anterior approach to RARP. ⁸

Similarly, proponents of the anterior approach argue for distinct advantages compared with the posterior approach. Some claim the distance between the posterior bladder neck and SVs is reliably short. Further, with the anterior approach, traction on the SVs allows for them to roll up and away from the neurovascular bundle, potentially decreasing the risk of nerve injury. ⁸

We compared our experience between two surgeons, each with different preferences to the means of SV dissection. Both surgeons were robotic-naïve and therefore at the bottom of their learning curves at the onset of this study. We found that there was no significant difference in the patient populations undergoing an anterior or posterior dissection. Further, we found no significant differences in intraoperative or 30-day perioperative outcomes.

When the population was broken into quartiles of prostate volumes, however, the posterior surgical approach offered a significant advantage of shorter console times in patients in the third and fourth quartiles. We think that it is these patients with larger prostate sizes who are more likely to have unfavorable prostate anatomy for the anterior dissection. This larger prostate size may add complexity to the anterior dissection, and some element of working in a hole is unavoidable in large prostate glands.

Two limitations to our study deserve mention. Our database consisted only of 30-day outcomes after RARP and therefore does not consider functional outcomes of continence and potency. With a theoretical advantage suggested by some with the anterior approach, we were not able to elucidate functional advantages given the short-term follow-up available for review. In addition, the anterior and posterior approaches are performed by different surgeons at our institution. Given that these were both robotic-naïve surgeons and their overall console times for all patients were not different, we think the advantage in console time of the posterior approach in larger prostate glands reflects the ability to eliminate difficulty with unfavorable anatomy by the posterior approach. We plan to perform a single-surgeon prospective study to limit the bias and further investigate the two approaches to RARP.

Conclusions

Despite the widespread application of RARP, there is no literature that addresses which surgical approach is most advantageous. In our experience, the posterior approach offers shorter operative times in patients with large prostate glands while overall outcomes remain the same between the two approaches.