Extraperitoneal single-port robot-assisted radical prostatectomy: Short-term outcomes and technique description

Abstract

Purpose

We evaluated the feasibility, safety, and learning curve of extraperitoneal single-port robot-assisted radical prostatectomy (SP-RARP) and introduced innovative surgical techniques to maintain the instrument positions during the procedures.

Materials and Methods

A cohort of 100 patients underwent extraperitoneal SP-RARP at our institution from December 2021 to April 2023. The procedures were performed by an experienced urology surgeon utilizing two surgical techniques for dissecting the posterior aspect of the prostate—“changing instrument roles” and “using camera inversion”—to prevent positional shifts between the camera and instruments.

Results

The mean operation time for SP-RARP was 93.58 minutes, and the mean console time was 65.16 minutes. The mean estimated blood loss during the procedures was 109.30 mL. No cases necessitated conversion to multi-port robot, laparoscopy, or open surgery, and there were no major complications during the hospital stay or in the short-term follow-up. Early outcomes of post-radical prostatectomy indicated a biochemical recurrence rate of 4.0% over a mean follow-up duration of 6.40 months, with continence and potency recovery rates of 92.3% and 55.8%, respectively. Analysis of the learning curve showed no significant differences in operation time, console time, and positive surgical margin rates between the initial and latter 50 cases.

Conclusions

Extraperitoneal SP-RARP is a feasible and safe option for the treatment of localized prostate cancer in skilled hands. Continued accrual of cases is essential for future comparisons of SP-RARP with multiport approaches.

Graphical Abstract

INTRODUCTION

In 2023, prostate cancer remained the most frequently diagnosed cancer among men in the United States, reporting 288,300 new cases and approximately 34,700 deaths [1]. Likewise, the incidence of prostate cancer in South Korea continues to rise, currently the most common cancer among men with 22,837 new cases and around 2,425 deaths [2,3]. The increasing prevalence of prostate cancer underscores the growing importance of surgical interventions. Systematic reviews of retrospective data have shown that robot-assisted techniques provide superior outcomes compared to conventional open surgeries in terms of erectile function preservation, urinary continence, complication minimization, and oncological effectiveness [4,5]. Over the last twenty years, the acceptance and adoption of robot-assisted radical prostatectomy (RARP) as a minimally invasive strategy for managing localized prostate cancer have significantly increased [6].

In 2018, the da Vinci single-port (SP) surgical system was introduced in the United States, offering potential benefits like enhanced visualization, improved cosmetic results, and reduced postoperative pain [7]. When considering the surgical approach, the extraperitoneal approach, despite its limited working space and lesser familiarity with intra-abdominal landmarks, provides advantages by avoiding the peritoneal cavity, reducing bowel manipulation, preventing ileus, and minimizing abdominal gas distension [8]. And the unique attributes of the da Vinci SP system make it particularly apt for the extraperitoneal approach in SP-RARP, enhancing its efficacy [7,9,10].

In Korea, after introducing the SP robot platform in 2019, it was adopted at our institution (Seoul St. Mary’s Hospital) in 2021. Over the past eighteen months, the use of SP robots for radical prostatectomies has increased substantially, now accounting for about one-third of all such procedures at the facility. This study investigates the outcomes of 100 cases performed by a single surgeon and explores the learning curve associated with extraperitoneal SP-RARP. Additionally, this study examines a surgical approach minimizing instrument changes by emphasizing role changes rather than manipulating instrument and camera positions. This approach differs from the conventional method of frequently switching instruments and the camera during each surgical step.

MATERIALS AND METHODS

1. Data collection

This retrospective analysis was sanctioned by the Institutional Review Board of Seoul St. Mary’s Hospital (approval number: KC23RISI0574) and the written informed consent was waived due to the study’s retrospective design. It encompassed 100 patients who underwent SP-RARP from December 2021 to April 2023. The surgeries were undertaken by a urology surgeon well-versed in robot-assisted surgeries, conducting over 2,000 successful da Vinci multi-port robotic cases. All patients underwent preoperative imaging, including multiparametric prostate magnetic resonance imaging (MRI), abdomen/pelvic computed tomography (CT), and bone scans. Prostate volumes were calculated using MRI measurements with the formula: length×width×height×0.52 [11,12]. Pre-surgery, prostate-specific antigen (PSA) levels were measured, and subsequent follow-ups were conducted at 1, 3, 6, 9, and 12 months post-operation. SP-RARP was chosen for patients with prostate masses under 50 g that did not require lymphadenectomy. Patients suspected of cT3 on preoperative MRI or those who had received neoadjuvant hormonal therapy were excluded, except for instances where previous abdominal surgeries had been performed—this necessitated the selection of extraperitoneal SP-RARP due to potential complications from intra-abdominal adhesions in multi-port surgeries. Various perioperative parameters were assessed including operation time, console time, estimated blood loss (EBL), conversion rates, length of postoperative hospital stay, and complications. Complications were classified according to severity using the Clavien–Dindo system [13].

For the early outcome data, trifecta components of post-radical prostatectomy such as biochemical recurrence (BCR) rate, urinary continence, and sexual potency were appraised [14]. BCR was defined as serum PSA level reaching or exceeding 0.2 ng/mL with showing an increase over two consecutive measurement. Continence was defined as the absence of the need for protective pads, and potency was determined by the ability to achieve and maintain an erection sufficient for successful intercourse. The Sexual Health Inventory for Men (SHIM) score, where a score of ≥17 indicates restored potency, was used to assess potency during the postoperative follow-up. The administration of phosphodiesterase-5 inhibitors was not considered in evaluating potency.

2. Surgical procedures and techniques

A vertical incision, measuring 3–5 cm, was made 5 cm superior to the symphysis pubis. The abdominal planes were meticulously dissected until the anterior rectus fascia was reached. Blunt dissection using the index finger and a balloon catheter facilitated the creation of the extraperitoneal space, into which approximately 400 mL of air was introduced to establish the preperitoneal working area (Fig. 1A). Subsequently, the operating table was adjusted to the Trendelenburg position, and a multi-purpose port was inserted at the incision site, supporting the floating trocar technique. This allowed the metal port to be withdrawn from the body, enhancing operability near the trocar insertion site and facilitating specimen removal. However, a disadvantage of the multi-purpose port is the potential leakage of CO₂ gas [15]. An assist port was then positioned 3–5 cm to the left lateral side of the incision site, utilizing a 10 mm trocar (Fig. 1B). At the 12 o’clock position on the robotic arm, a camera was installed; at the 9 o’clock, Maryland bipolar forceps were operated by the surgeon’s left hand, and at the 6 o’clock position, Cadiere forceps were used, with monopolar curved scissors in the right hand at the 3 o’clock position (Fig. 2A). The dissection technique closely resembled that of the conventional extraperitoneal multiport RARP.

Fig. 1. Preparation of SP-RARP (single-port robot-assisted radical prostatectomy). (A) A vertical incision, measuring 3–5 cm, was executed 5 cm superior to the symphysis pubis and below the umbilicus. Subsequently, a balloon catheter facilitated the creation of the extraperitoneal space. (B) Through the incision, a floating docking port was inserted. Subsequently, a 25 mm single-port trocar was introduced into the docking port, secured by an entry guide. To the left lateral side of the incision site, an assist port was positioned using a 10 mm trocar.

Fig. 2. Conventional instrument position of single-port robot-assisted radical prostatectomy (SP-RARP) for dissecting the posterior aspect of prostate. (A) In conventional SP-RARP, the camera was inserted at the 12 o’clock position. In the operator’s left hand (9 o’clock position), Maryland bipolar forceps were utilized (‘M’), while Cadiere forceps were employed at the 6 o’clock position (‘C’). In the right hand (3 o’clock position), monopolar curved scissors were manipulated (‘S’). (B) While dissecting the posterior aspect of the prostate, the positions of the Cadiere forceps and the camera were altered to enhance the procedure. The entire port configuration was rotated 180°, transitioning the camera position from 12 o’clock to 6 o’clock. Consequently, the Maryland forceps and monopolar scissors had to be repositioned by assistant to maintain their prior positions.

In conventional SP-RARP, changing the positions of the instruments according to the surgical steps is necessary [9,16]. For instance, to dissect the posterior aspect of the prostate, the positions of the Cadiere forceps and the camera were swapped to 12 o’clock and 6 o’clock, respectively (Fig. 2B). With only one channel available for the camera, the entire port had to be rotated 180° to shift the camera from 12 o’clock to 6 o’clock. Consequently, the positions of the Maryland forceps and monopolar scissors on the left and right also required adjustments.

Then, for the apex resection, the positions were reverted, placing the camera at 12 o’clock and the Cadiere forceps at 6 o’clock. During these adjustments, the surgeon continued utilizing the Maryland forceps for dissection and the Cadiere forceps for traction. Yet, in this study, instead of changing the camera position with the robot arms, the Maryland forceps at 9 o’clock were used for the traction of the seminal vesicle, while the Cadiere forceps served as the primary working arm for dissecting the posterior aspect of the prostate (Fig. 3).

Fig. 3. Role change of instruments. In our study, Cadiere forceps were employed for dissection and Maryland forceps for traction during the seminal vesicle and posterior aspect dissection, without changing the instruments’ positioning.

In situations where access was challenging or visualization was compromised, despite the method described in Step 3, we opted against using the strategy depicted in Fig. 2B. Rather, we employed the “inversion technique” a distinctive feature of SP, involving a 180° rotation of the “instrument drive” while keeping the camera and instruments inside the patient (Fig. 4). This rotation enables the positioning of the camera beneath and the Cadiere forceps above. Importantly, this vertical inversion does not alter the left-right configuration of the instruments.

Fig. 4. Inversion technique during posterior aspect dissection. Utilizing this method, the camera was positioned below and the Cadiere forceps above. This vertical inversion did not modify the left-right configuration.

For apex resection, we utilized the “cobra mode,” a unique SP feature that enhances visibility in the deep pelvic regions. This mode not only improved visualization but also facilitated effective procedure execution despite the constraints imposed by instrument design.

Following the prostate resection, the urethra-vesical anastomosis was executed. At this stage, the 3 o’clock and 9 o’clock robotic arms were changed to the needle holders. Three reconstruction techniques were employed to restore the normal anatomical and functional relationships in the pelvic floor, thus facilitating early continence recovery. First, the “posterior reconstruction” involved suturing the remnant Denonvilliers’ fascia, posterior detrusor, and posterior rhabdosphincter (Fig. 5A). This was followed by the “anterior reconstruction” which involved suturing the muscular fibers of the bladder neck to the periurethral tissues (Fig. 5B). Lastly, the “pubourethral suspension stitch” was executed, suspending the urethra to the periosteum of the pubic bone (Fig. 5C).

Fig. 5. Three reconstruction techniques for achieving early continence recovery. (A) Posterior reconstruction (modified Rocco stitch): A running continuous absorbable suture was employed to reapproximate the remnant of Denonvillier’s fascia, posterior detrusor, and posterior rhabdosphincter prior to the completion of the vesicourethral anastomosis. (B) Anterior reconstruction: The anterior bladder was reapproximated by suturing the muscular fibers of the bladder neck to the periurethral tissues. (C) Pubourethral suspension stitch: The urethra was suspended by anchoring the supportive tissues ventral to the urethra to the periosteum of the pubic bone.

After the completion of the anastomosis and reconstructions, the specimen was removed through the incision site, and a Jackson–Pratt (JP) catheter was inserted through the assist trocar site. The JP catheter was removed on postoperative day 3 unless significant complications emerged during the postoperative care.

RESULTS

A retrospective analysis was conducted on 100 patients who underwent extraperitoneal SP-RARP. We evaluated the learning curve by comparing the first 50 cases with last 50 cases.

1. Patient and disease characteristics (preoperative features)

The mean age of the patients was 66.47±6.70 years, with a mean body mass index of 24.49±2.80 kg/m². The mean preoperative PSA, measured the day before surgery, was 8.56±7.57 ng/mL, and the mean prostate volume was 35.62±14.51 cc. The clinical stage assessed by MRI revealed T2a as the most common stage (68 patients, 68.0%), followed by T2c (19 patients, 19.0%). No lymph node or bone metastases were detected on preoperative CT and bone scans. Among the biopsy results, the Gleason score of 7 (3+4) was predominant, observed in 48 patients (48.0%), followed by the Gleason score of 7 (4+3), observed in 27 patients (27.0%). According to the National Comprehensive Cancer Network (NCCN) 2019 risk classification, the most frequent risk group was favorable intermediate, involving 41 patients (41.0%), followed by high risk in 22 patients (22.0%) (Table 1).

Table 1. Demographics and preoperative characteristics.

Variable			Value
Age (y)			66.47±6.70
Height (cm)			168.81±6.06
Weight (kg)			69.86±9.33
BMI (kg/m2)			24.49±2.80
PSA (ng/mL)			8.56±7.57
MRI
	Prostate size (cc)		35.62±14.51
	T-stage
		T2a	68 (68.0)
		T2b	2 (2.0)
		T2c	19 (19.0)
		T3a	11 (11.0)
		T3b–T4	0 (0.0)
Biopsy
	Gleason score
		6 (3+3)	12 (12.0)
		7 (3+4)	48 (48.0)
		7 (4+3)	27 (27.0)
		8 (4+4)	8 (8.0)
		9 (4+5)	5 (5.0)
		9 (5+4), 10 (5+5)	0 (0.0)
NCCN risk (version, 2019)
	Low		14 (14.0)
	Favorable intermediate		41 (41.0)
	Unfavorable intermediate		21 (21.0)
	High		22 (22.0)
	Very high		2 (2.0)

Values are presented as mean±standard deviation or number (%).

BMI, body mass index; PSA, prostate-specific antigen; MRI, magnetic resonance imaging; NCCN, National Comprehensive Cancer Network.

2. Operative and postoperative characteristics

The mean operation time for the SP-RARP procedure was 93.58±16.96 minutes, with a mean console time of 65.16±14.22 minutes. The mean EBL during the surgery was 109.30±95.58 mL. Importantly, no case required conversion to multi-port robot-assisted surgery, laparoscopy, or open surgery during the procedure.

During the hospitalization and short-term follow-up periods, no complications were classified as Clavien–Dindo grade ≥3. There were three instances of grade 1 complications: two patients experienced swelling in their legs and penis, and another patient experienced nausea and vomiting after the surgery. None of the patients required a transfusion.

Histopathological examination revealed that 76 patients (76.0%) were at stage T2, while 19 patients (19.0%) and 5 patients (5.0%) were at stages T3a and T3b, respectively. The positive surgical margin (PSM) rates were highest for stage T3b, with 4 out of 5 patients (80.0%) affected, while stage T3a showed a PSM rate of 42.1%, with 8 out of 19 patients affected. Among those at stage T2, only 10 patients (13.2%) exhibited PSM. The mean length of hospital stay post-surgery was 4.02±0.40 days (Table 2).

Table 2. Intraoperative, postoperative, and pathology data.

Variable		Value
Operation time (min)		93.58±16.96
Console time (min)		65.16±14.22
Estimated blood loss (mL)		109.30±95.58
Complication (Calvien–Dindo grade)		3
	Grade 1–2	3
	Grade ≥3a	0
Pathology
	T2	76 (76.0)
	T3a	19 (19.0)
	T3b	5 (5.0)
Positive surgical margin rate		22/100 (22.0)
	T2	10/76 (13.2)
	T3a	8/19 (42.1)
	T3b	4/5 (80.0)
Postoperative hospital day (d)		4.02±0.40

Values are presented as mean±standard deviation, number only, or number (%).

3. Early outcome

We analyzed the trifecta outcomes following radical prostatectomy. The mean follow-up period was 6.40 months, with the overall BCR rate recorded at 4.0% (Fig. 6). Among the 52 patients followed up for at least 9 months, we evaluated their urinary continence and sexual potency. It was noted that 48 (92.3%) of the 52 patients regained urinary continence nine months post-surgery. Furthermore, during the same period, 29 (55.8%) of the 52 patients reported restored erectile function, as indicated by a SHIM score of ≥17 (Table 3).

Fig. 6. Kaplan–Meier estimation of the biochemical recurrence (BCR) survival rate after extraperitoneal SP-RARP (single-port robot-assisted radical prostatectomy).

Table 3. Early outcomes of extraperitoneal SP-RARP.

Variable		Value
Biochemical recurrence		4/100 (4.0)
Continence		48/52 (92.3)
	1 month	10/52
	3 months	30/52
	6 months	42/52
	9 months	48/52
Potency (SHIM score ≥17)		29/52 (55.8)
	1 month	12/52
	3 months	18/52
	6 months	25/52
	9 months	29/52

Values are presented as number (%) or number only.

SP-RARP, single-port robot-assisted radical prostatectomy; SHIM, Sexual Health Inventory for Men.

4. Learning curve

Regarding operation and console times, the first 50 cases mean 93.98 minutes and 64.74 minutes, respectively, whereas the last 50 cases mean 93.18 minutes and 65.58 minutes, showing no statistically significant differences (p=0.815 and p=0.769, respectively). The EBL was slightly higher in the last 50 cases, mean 121.40±120.02 mL, compared to 97.20±61.28 mL in the first 50 cases; however, this difference was not statistically significant (p=0.280). Concerning PSM rates, the first 50 cases had 13 cases (26.0%) of PSM, while the last 50 cases had 10 cases (20.0%) of PSM. For the pathology stage T2, the PSM rate was 15.4% in the first 50 cases and 10.8% in the last 50 cases. Although there was a decrease in PSM rates in the later cases, the difference was not statistically significant (p=0.339 and p=0.601, respectively). Furthermore, there was no significant difference in the mean postoperative hospital stays, which were 4.04±0.45 days for the first 50 cases and 4.00±0.35 days for the last 50 cases (Table 4).

Table 4. The learning curve of SP-RARP.

Variable		First 50 cases	Last 50 cases	p-value
Operation time (min)		93.98±15.42	93.18±18.51	0.815
Console time (min)		64.74±12.20	65.58±16.10	0.769
Estimated blood loss (mL)		97.20±61.28	121.40±120.02	0.280
Positive surgical margin rate		13/50 (26.0)	10/50 (20.0)	0.339
	T2 margin positive	6/39 (15.4)	4/37 (10.8)	0.601
Hospital day after surgery (d)		4.04±0.45	4.00±0.35	0.621

Values are presented as mean±standard deviation or number (%).

SP-RARP, single-port robot-assisted radical prostatectomy.

DISCUSSION

The utilization of the SP robot platform for prostate cancer has been extensively investigated worldwide, demonstrating promising outcomes regarding feasibility and safety. In conventional SP-RARP, however, the assistant must adjust the positions of the instruments in the surgical field at various procedure stages. While not overly time-consuming, this adjustment process is undoubtedly cumbersome. The technique in this study aims to minimize frequent instrument changes to alleviate the associated inconvenience. The primary objective is to introduce techniques and present initial short-term outcomes, rather than to establish superiority of a new method. Additionally, this technique requires proficient use of the Cadiere forceps as a dissector, similar to skills required for the Maryland instrument, which demands substantial experience in robot-assisted surgery.

We offer two practical surgical tips for our SP-RARP procedures. Firstly, employing cobra mode after a 180° rotation enhances the viewing angle towards the prostate's posterior aspect, thus facilitating access to deeper areas near the apex. Secondly, to minimize internal collisions, avoid placing the camera too close to other instruments and ensure adequate spacing in narrow spaces. Surgeons often extend their wrists to maximize spacing, but this increases the risk of collision. If an internal collision occurs, loosening the excessively bent wrist angle when holding the instrument with both arms is helpful.

Considering our experience with multi-port RARP using a transperitoneal approach, we initially adopted the same approach for SP-RARP. However, we recognized the advantages of the extraperitoneal approach for radical prostatectomy such as reduced peritoneal irritation, minimal bowel manipulation, and a less steep Trendelenburg position due to natural retraction of bowels and intra-abdominal fat caused by pelvic insufflation. Moreover, in patients with a history of extensive abdominal or pelvic surgeries, where significant adhesions are anticipated, accessing the intraperitoneal space can be quite challenging [17]. Therefore, we currently perform SP-RARP using an extraperitoneal approach.

Regarding perioperative factors, SP-RARP demonstrated relatively shorter surgical times, with a mean operation time of 93.58 minutes and a console time of 65.16 minutes, when compared to previously described times [16,18,19]. Additionally, the EBL was relatively low, mean 109.30 mL [16,18,19,20]. These favorable outcomes can be attributed to the surgeon's extensive experience in performing a high volume of multiport robot surgeries. Moreover, the surgical team, consisting of skilled scrub nurses and medical assistants, played a crucial role in achieving these results, having accumulated over 1,000 cases of experience in multi-port procedures. There were no cases that required conversion to laparoscopy or open surgery, further indicating the feasibility of the SP approach. The procedure’s safety was reinforced by the absence of any significant complications (grade ≥3a) or the need for blood transfusion during or after the surgery.

Regarding the learning curve, no statistically significant difference was found between the last 50 cases and the first 50 cases. Although EBL was slightly higher in the last 50 cases, the difference was not statistically significant. The mean estimated blood loss in the last 50 cases was 121.40 mL, which is not substantial and therefore does not raise significant concerns for patients. According to the data analysis, none of the 100 patients required a blood transfusion after surgery.

For the PSM rate, the p-value did not indicate a statistically significant difference between the initial 50 cases and the final 50 cases. Nonetheless, the overall rate was 22.0%, specifically 13.2% for pathological stage T2, which is comparable to or lower than the rates reported in other studies [16,18,19,20]. This implies that extraperitoneal SP-RARP is more effective for localized prostate cancer than for advanced cases. Proficiency in SP-RARP can be achieved by high-volume experts without significant learning curves.

This study has several limitations. Firstly, the retrospective design could introduce selection bias. Like other singlecenter retrospective studies on SP surgery, extraperitoneal SP-RARP may encounter challenges with large prostate sizes or substantial extraprostatic extension, where multiport robot surgery or transperitoneal approaches might be more suitable. Secondly, a high level of technical expertise is required for the successful implementation of the extraperitoneal approach [9,18]. Surgeons lacking extensive experience in multi-port robot systems and laparoscopic prostatectomy may face difficulties due to the confined space and the absence of indicator organs [18]. Furthermore, although the cobra mode operation is relatively straightforward, the surgical technique employed in this study, which involves the inversion technique and a role shift among robotic instruments, could pose challenges for surgeons inexperienced in robotic surgery. Thirdly, extraperitoneal SP-RARP was generally selected for patients who did not require pelvic lymphadenectomy. Nevertheless, some patients at high risk based on NCCN criteria were included due to previous abdominal surgeries and the anticipation of intra-abdominal adhesions. For such cases, choosing an extraperitoneal approach with a single-port robot was deemed more appropriate than a transperitoneal approach using a multi-port robot. However, the omission of lymphadenectomy in these patients represents a limitation of this study.

CONCLUSIONS

We demonstrated the surgical procedure of SP-RARP without changing the position of the instruments. This method could potentially shorten surgical times by minimizing the need to change the camera and instruments positions during the posterior dissection and the apex resection. Moreover, our data indicate that skilled, high-volume surgeons can gain proficiency in SP-RARP without significant learning challenges. Given the findings, SP-RARP emerges as a viable and safe option for the treatment of localized prostate cancer, particularly when performed by surgeons with extensive experience. As we expand our case volume of SP-RARP, we aim to evaluate its outcomes against those of the multi-port robotic techniques using propensity score matching.