Third Prize: Perineal Robot-Assisted Laparoscopic Radical Prostatectomy: Feasibility Study in the Cadaver Model

Abstract

Purpose:

To evaluate the feasibility of perineal robot-assisted laparoscopic radical prostatectomy (P-RALP) in the cadaver model.

Methods:

The prostate was assessed by ultrasonography and cystoscopy in the lithotomy position. After incision and subcutaneous dissection, a single-port device was placed and the robot was docked. The rectourethralis muscle was divided and the levator ani fibers were split. The Denonvilliers fascia was incised and the posterior prostate and seminal vesicles were dissected. The apex was dissected and the urethra was transected. The anterior and lateral planes were dissected and the prostate pedicles were clipped. The prostate was freed from the bladder neck and the vesicourethral anastomosis was performed. The robot was undocked and the wound was sutured in layers. Cystoscopy confirmed integrity of the anastomosis. The specimen was sent for histopathology examination.

Results:

Nerve-sparing P-RALP was successfully completed in three cadavers. Median time for setting was 23 minutes. Time for posterior dissection was 15 minutes. Dissection of the apex and section of the urethra took 9 minutes. Time for anterolateral dissection was 14 minutes. Time for bladder neck dissection was 7 minutes. Vesicourethral anastomosis took 8 minutes. Total operative time was 89 minutes. The prostate capsule was grossly intact and histopathology examination was negative for prostatic tissue in all distal urethral sections and in two of three bladder neck sections.

Conclusions:

P-RALP is feasible in the cadaver. Future studies should evaluate the feasibility of lymph node dissection through the same incision, clinical feasibility, and prospective comparisons with standard techniques.

Introduction

Open perineal radical prostatectomy (PRP) was first described by Young¹ in 1905 and remained the most common surgical approach for prostate cancer until the mid-1970s. The retropubic technique, however, initially described by Millin² in 1947, was popularized in the early 1980s, thanks to the development of the anatomic approach by Walsh and associates.³ Still during the 1980s, Weiss and colleagues⁴ applied the techniques of cavernous nerve sparing described by Walsh and coworkers³ to PRP. For open surgery, the retropubic approach currently represents the preferred technique by most urologic surgeons, although this preference seems to be based more on surgeon habits rather than on evidence-based medicine.

Robot-assisted laparoscopic radical prostatectomy (RALP) was first described in Europe in the early 2000s,^5,6 and its use rapidly expanded over the last 12 years. Currently, RALP represents the most commonly performed surgical approach for prostate cancer in the United States.⁷

We are not aware of any previous publication investigating the applicability of the robot for the perineal approach in prostate cancer. We evaluate the feasibility of perineal RALP (P-RALP) in the cadaver model.

Methods

Procedure

P-RALP was performed in three male cadavers. Preoperative characteristics are shown in Table 1.

Table 1.

Preoperative Characteristics and Outcomes

BMI (Kg/m²)	27 (23–31)
Median prostate size (cc)^a	25 (22–28)
Median setup time (min)	23 (19–31)
Median time for posterior dissection (min)	15 (11–20)
Median time for apical dissection and section of the urethra (min)	9 (7–11)
Median time for anterolateral dissection (min)	14 (10–19)
Median time for bladder neck dissection and specimen extraction (min)	7 (6–9)
Median time for vesicourethral anastomosis (min)	8 (6–11)
Median total operative time (min)	89 (53–117)
Bilateral nerve sparing (%)	100
External urinary sphincter intact on postoperative cystoscopy (%)	100
Prostate capsule grossly intact (%)	100
Distal urethral margin negative for prostatic tissue (%)^b	100
Proximal urethral margin negative for prostatic tissue (%)^b	67

On transrectal ultrasonography.

On histopathology examination.

BMI=body mass index.

Instrumentation

For preoperative assessment of the prostate, we used a portable Pro Focus B ultrasound device with a transrectal probe (BK Medical, Herlev, Denmark) and rigid cystoscopy with a 19F sheath and 30-degree lens (Karl Storz, Tuttlingen, Germany), which was also used at the end of the procedure for evaluation of the anastomosis and external urethral sphincter integrity.

For perineal access, scalpel, tissue forceps, Metzenbaum scissors, Allis and right angle forceps, as well as Richardson retractors were used. A GelPOINT™ Mini Advanced Access Platform (Applied Medical, Rancho Santa Margarita, CA) was used, including an Alexis™ wound retractor and a GelSeal™ Cap (Applied Medical). The da Vinci Si™ system (Intuitive Surgical, Sunnyvale, CA) was used in a three-arm configuration. One 12-mm trocar (robotic scope), one 10-mm trocar (assistant), and two 8-mm robotic trocars were inserted through the GelSeal™ Cap in a diamond-shape configuration, with the 12-mm trocar at the bottom and the 10-mm trocar at the top (Fig. 1A). A 0-degree robotic scope was used. Robotic monopolar curved scissors (Hot Shears™) and robotic needle driver were used in the right hand. A robotic grasper (ProGrasp™ forceps) was used in the left hand.

FIG. 1.

Setup and preoperative prostate assessment. (A) Trocar configuration; (B) cystoscopic view of the prostate; (C) prostate transrectal ultrasonography; and (D) lithotomy position with steep Trendelenburg position.

Prostate assessment and cadaver positioning

The cadaver was placed in the lithotomy position. We performed digital rectal examination (DRE), cystoscopy, and transrectal ultrasonography (TRUS) preoperatively to estimate the size of the prostate (Figs. 1B, 1C). We then taped the cadaver to the surgical table and applied steep Trendelenburg (Fig. 1D).

Perineal access and robot docking

A 4 to 5 cm perineal incision was made, the subcutaneous tissue was dissected, and the central tendon was divided (Figs. 2A, 2B). A procedure analogue to the Belt approach was performed, retracting the external sphincter muscle superiorly (Fig. 2C).⁸ The single port device was inserted into the wound, and CO₂ insufflation was obtained (Fig. 2D). The robot was brought into the field and docked from behind the head. Considering a potential future clinical application, enough room for the anesthesiology team to access the head, neck, and chest of the patient is available from either side (Fig. 1D).

FIG. 2.

Incision, single-port device insertion, and robot docking. (A) Perineal skin incision; (B) central tendon; (C) external anal sphincter retracted anteriorly by sutures; and (D) robotic instruments through the single-port device.

Robotic procedure

The rectourethralis muscle was identified and divided. The bedside assistant provides crucial information to the console surgeon while performing DRE. The levator ani fibers were split aside, and the posterior aspect of the Denonvilliers fascia was identified and incised (Fig. 3A), preserving the neurovascular bundles intact. The posterior plane of the prostate, vas deferens, and seminal vesicles was dissected (Figs. 3B, 3C). The prostatic pedicles were clipped and divided (Fig. 3D).

FIG. 3.

Posterior plane dissection. (A) Incision of the Denonvilliers fascia; (B) exposure of the vas deferens and seminal vesicles; (C) left vas deferens section; and (D) right prostatic vascular pedicle control. RSV=right seminal vesicle; RVD=right vas deferens (partially exposed); LVD=left vas deferens; LSV=left seminal vesicle; P=prostate.

The prostatic apex was dissected, the urethra was transected, and the Foley catheter was clipped and cut (Figs. 4A–C). The proximal portion of the catheter was used as a handle for retraction (Fig. 4D). The anterior and lateral planes of the prostate were dissected (Fig. 5A). The bladder neck junction was identified and dissected away from the prostate (Fig. 5B). The catheter clip was removed to deflate the balloon and the specimen was separated from the bladder (Figs. 5C, 5D).

FIG. 4.

Apical dissection and section of the distal urethra. (A) Dissection of the prostatic apex (PA); (B) section of the urethra; (C) completion of the urethral sectioning; and (D) use of the Foley catheter stump as a handle for retraction. U=urethra; P=prostate; PPL=puboprostatic ligaments.

FIG. 5.

Anterior, lateral, and bladder neck dissection. (A) Anterior plane dissection; (B) bladder neck dissection; (C) specimen detached from the bladder neck (BN); and (D) BN and urethra (U) ready for anastomosis. P=prostate.

A second Foley catheter was inserted to guide the vesicourethral anastomosis, performed according to the van Velthofen method (Figs. 6A–D). The anastomosis was tested with instillation of 200 mL of saline in the bladder, with no evidence of leakage. The robot was undocked and the single-port device was removed.

FIG. 6.

Vesicourethral anastomosis. (A) Insertion of a second Foley catheter to guide the anastomosis; (B) traction on the catheter to assist the placement of the initial urethral suture at the 12 o'clock position; (C) first half of the anastomosis with running 4.0 polyglactin suture; and (D) completion of the anastomosis. BN=bladder neck; U=urethra.

The perineal fascial and subcutaneous planes were re-approximated and the skin incision was sutured (Fig. 7A). The Foley catheter was removed, and postoperative cystoscopy demonstrated integrity of both the anastomosis and the external urethral sphincter (Figs. 7B, 7C). The specimen was sent to pathology examination for evaluation of prostate capsule integrity as well as for the presence of prostatic tissue in the proximal (bladder neck) and distal urethral margins (apex) (Figs. 7D, 8A, 8B).

FIG. 7.

Wound closure, postoperative cystoscopy, and specimen. (A) Wound closure; (B) cystoscopic view showing intact anastomosis; (C) cystoscopic view showing intact external urethral sphincter (EUS); and (D) specimen removed. B=bladder; DU=distal urethra; SV=seminal vesicles; P=prostate.

FIG. 8.

Histopathology examination. (A) Apical section with no prostate tissue; and (B) bladder neck section showing few prostatic glands in one cadaveric specimen.

Results

In the three cadavers, a nerve-sparing P-RALP was successfully completed with no injuries to surrounding structures. Median prostate size estimated by TRUS was 25 cc. The results are summarized in Table 1. Median time for positioning, open perineal Access, and robot docking was 23 minutes. Median time for posterior dissection was 15 minutes. Median time for dissection of the apex and section of the urethra was 9 minutes. Median time for anterolateral dissection was 14 minutes. Median time for bladder neck dissection and specimen extraction was 7 minutes. Median time for vesicourethral anastomosis was 8 minutes. Median total operative time was 89 minutes. Macroscopic evaluation of the specimens showed integrity of the prostate capsule (Fig. 7D). On histopathology examination, the distal margins were negative for prostatic tissue in all cases (Fig. 8A). The proximal margin (bladder neck) was positive for prostatic tissue in one specimen (Fig. 8B).

Discussion

To the best of our knowledge, this is the first description of a P-RALP technique. We found the procedure to be feasible in the cadaver model. Currently, the majority of radical prostatectomies in the United States are performed with robotic assistance.⁷

Although the most largely used approach for open radical prostatectomy is the retropubic, there are no randomized studies to date showing superiority over the perineal approach in terms of cancer control and continence rates.^9

–12

Reported advantages of the perineal approach include shorter operative time and hospital stay,¹³ lower cost for patients who do not need bilateral pelvic lymph node dissection (BPLND),¹⁴ lower postoperative incidence of anastomotic stricture¹⁵ and inguinal hernia,¹⁶ as well as lower blood loss and transfusion rates.^9,13 In the perineal approach, there is no need for the penile dorsal vein complex sectioning.

Disadvantages reported include higher rates of rectal injury⁹ and difficult nerve-sparing for large prostates.¹⁷ During the posterior dissection, the bedside assistant has a critical role while performing DRE and providing feedback to the console surgeon about the correct plane of dissection. This helps to minimize the risk of rectal injury. It is important also, however, to avoid dissecting too anteriorly to avoid inadvertent injury to the bulbar urethra before the identification of the prostate.

Until recently, one of the major disadvantages attributed to perineal radical prostatectomy was that patients requiring BPLND needed to have it performed through a separate access, usually via laparoscopy. Saito and Murakami,¹⁸ however, described a technique for BPLND through the same perineal incision, using several retractors for direct view or laparoscopic assistance. They obtained a median of eight lymph nodes via the perineum in 20 patients who underwent PRP.

Keller and colleagues¹⁹ reported extended BPLND via the same perineal incision in 90 patients who underwent PRP. After the prostate removal, they performed the extended BPLND under direct vision using a self-retaining system, retracting the bladder medially. Their technique yielded the retrieval of 19 lymph nodes on average, with a mean operative time of 149 minutes. Lymphocele developed in seven (7.8%) patients, with four (3.3%) of them needing treatment. The next goals with our technique are to evaluate in the cadaver the feasibility of robotic BPLND through the same perineal incision after prostate extraction and clinical feasibility.

Some authors found that RALP have lower estimated blood loss and transfusion rates in comparison with open retropubic radical prostatectomy, although the absence of randomized studies still limits definitive conclusions.^20

–23 Whether similar advantages could also be observed using the robot specifically for PRP is not clear yet and must be further studied. Horuz and associates²⁴ studied different ultrasonography parameters in 50 patients undergoing open PRP to identify those associated with difficulty of the operation, determined by a score composed of operative time, estimated blood loss, and surgeon subjective judgment. They found that a prostate volume >40 mL and a probe-divergence angle <45 degrees (the angle between the vertical axis and the oblique plane obtained when directing the probe toward the base of the prostate during suprapubic ultrasonography) were independent predictors for a more difficult procedure.

In an endoscope-assisted PRP technique, investigators from the same institution described the use of a Collins knife to cut under direct vision the prostate-vesical junction, which is regarded as one of the most difficult steps in radical prostatectomy.²⁵

In our study, the only margin positive for prostatic tissue was located exactly at the prostate-vesical junction in one cadaver. This was also the largest prostate (28 cc), while the two other glands were 22 and 25 cc on preoperative TRUS. Because of the small sample size, however, we cannot claim any correlation between prostate size and margin status. Potential technical benefits of P-RALP over open PRP include the magnified view as well as the long, stable, and articulated robotic instruments, which may help to minimize the difficulty of performing a procedure in such a narrow and sometimes deep surgical field. In our experiments, we were able to complete the procedures with a small incision (4–5 cm), just enough for specimen extraction. Minimizing the incision could also potentially decrease postoperative pain and analgesia requirement.

To justify the P-RALP approach, we should also foresee potential advantages over the standard RALP technique. From a purely anatomic standpoint, a perineal approach makes complete sense, because it provides a more direct access to the prostate than the anterior abdominal wall. Potential clinical advantages include the elimination of the three first steps commonly performed in RALP (bladder mobilization, endopelvic fascia opening, and dorsal vein complex control), which could theoretically result in shorter operative time and lower blood loss.

As a completely extraperitoneal approach, P-RALP virtually eliminates risks of injury to the small bowel or major vessels during trocar placement, which, despite rare, can be catastrophic. It also allows avoidance of having to deal with extensive adhesions in patients with previous multiple surgeries or repair of abdominal wall defects with mesh. Obese patients often impose a technical challenge during standard RALP. A greater incidence of case abortion because of pneumoperitoneal pressure and excessive airway pressures has been reported in this group of patients.²⁶ Although P-RALP uses CO₂ insufflation to improve visualization, it eliminates the need for pneumoperitoneum and its possible complications, which may make it an attractive alternative for specific patients.

We must acknowledge limitations of our study. These were experimental cadaveric procedures, conducted by an experienced robotic surgeon and robotic/laparoscopy fellows. Although the cadaver provides us an optimal evaluation of the anatomy, the absence of bleeding substantially impairs our ability to assess the safety of this procedure. This is a proof of concept study, however. Its main merit is to propose a different application of the surgical robot for a well-known approach.

Conclusions

P-RALP is feasible in the cadaver model. Future studies should evaluate the feasibility of robotic BPLND through the same incision as well as clinical feasibility, safety, and efficacy. Afterward, prospective studies will be needed to compare this approach with standard techniques.

Footnotes

Disclosure Statement

Oktay Akça is funded by TUBITAK. No competing financial interests exist for the remaining authors.

Abbreviations Used

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