Faster both in operative time and functional recovery by the extraperitoneal daVinci SP- based robot-assisted radical prostatectomy: A propensity score matching analysis compared to transperitoneal multiport counterpart

doi:10.21203/rs.3.rs-3995169/v1

We aim to investigate the peri-operative outcomes after extraperitoneal single-port based robot-assisted radical prostatectomy (eSP-RARP) utilizing the da Vinci SP system compared to conventional transperitoneal multi-port counterparts (tMP-RARP), in an era when pelvic lymph node dissection (PNLD) was omitted for the node-negative case. With exclusion criteria of volume + 50g, suspicious rectal invasion, and node-positive disease given relatively weak grasping power and limited range of motion from the current SP system, 50 consecutive patients (Since December 2021) with localized prostate cancer underwent eSP-RARP by a single urologist maintaining identical surgical technique for 100 consecutive tMP-RARP cases (Since December 2020). Given initial selection criteria, each group was matched to a 1:1 ratio based on the risk-stratification parameters and the prostate volume. The operative time, which was maintained in each group during the study period, was significantly faster in eSP-RARP groups than in tMP-RARP (149.2 vs. 163.2 minutes, p = .025), while the weight of the removed specimen (27.1 vs. 29.0 g, p = .420) and margin positivity (14.7% vs. 11.7% in pT2, p = .812) were similar. The gas-out (1.5 vs. 1.88 days, p = .003) and solid diet dates (2.26 vs. 3.22 days, p < .001) were faster in the eSP-RARP group. The single-pad continence dates (30.5 vs. 51.9 days, p = .145) and zero-pad continence dates (105.5 vs. 146.2 days, p = .210) were identical. 90-day single-pad continence rate was 92% vs. 82% (p = .142, 52% vs. 56% in zero-pad continence). Based on these, daVinci SP-based RARP restored bowel function faster with shorter operative time through an extraperitoneal approach than the conventional transperitoneal multi-port counterpart while maintaining similar incontinence outcomes in cases without a routine PNLD.

With the expansion of prostate-specific antigen (PSA) testing, many prostate cancers (PCa) are detected in localized stages, and prostatectomy is increasingly performed in older men [1–2]. To facilitate postoperative functional recovery and reduce surgery-related morbidity, several modifications in approaches to the prostate have been suggested [3], along with technological advances, including the introduction of single port-based robot-assisted radical prostatectomy (SP-RARP).; Retzius-sparing, transvesical, peritoneal, and extraperitoneal way has been proposed as alternatively to the conventional transperitoneal one that became commonplace in the era of the multiport-based robot-assisted radical prostatectomy (MP-RARP).

Among these, comparing the extraperitoneal and transperitoneal approaches has been attempted since the early 2000s, with two meta-analyses [7, 8], including three RCTs [4–6], similarly reporting an advantage of the extraperitoneal one in terms of complications. Additionally, the extraperitoneal approach applied for the SP-RARP is expected to reduce operative time due to the relatively small area required for the retroperitoneal dissection before robotic docking and omitting the need for anterior bladder dissection. However, two recently published multicenter studies to date that compared the performance of extraperitoneal versus transperitoneal approaches within the SP platform have reported completely conflicting operative time outcomes [3, 9, 10]. They nonetheless included many cases with pelvic lymph node dissections (PLND), which would be expected to favor the transperitoneal approach, which is likely a compounding factor. Therefore, we sought to compare the peri-operative outcomes between eSP-RARP and transperitoneal MP-RARP in a single surgeon without a change in surgical technique since 2020, from when the results of two RCTs for the role of PNLD were reported [11, 12] and the routine PNLD was omitted for the node-negative cases.

The enrollment of the patient and data acquisition

daVinci SP robotic surgical system (Intuitive Surgical, Sunnyvale, CA) was introduced in our institution in December 2021. After the initial four cases with a transperitoneal approach, 50 consecutive patients with localized PCa underwent extraperitoneal SP-RARP (eSP-RARP) applying the daVinci SP system until December 2022. After approval from the institutional review board (####-2023-08-035), the retrospective data from those patients, as well as the data from 100 consecutive transperitoneal MP-RARP (tMP-RARP) performed since December 2020, was obtained from their medical records, including surgical, pathological, and functional recovery especially on the bowel and continence function until six months after surgery.

The recovery of continence was acquired from the direct question by the physician to the patient during the outpatient visit. Given the discordance between the zero-pad and social-pad (single-pad) status [13], the first date for single-pad and zero-pad was asked for each visit until the patient replied that there was no leakage. Each patient's admission nurse investigated the diet date and gas out date. Under Korea's mandatory medical insurance, patients were routinely discharged with catheters removed on the fifth day after surgery.

The inclusion criteria for eSP-RARP in our institution was localized PCa under the radiologic evaluation, including abdominal computed tomography (CT), multiparametric prostate magnetic resolution imaging (MRI), and bone scan, all of which were a routine evaluation under the Korean medical insurance system. The exclusion criteria in this series for eSP-RARP were 1) prostate size of more than 50g by ultrasonographic estimation given relatively weak grasping power than the multi-port robotic system and limited small incision for the eSP-RARP that maximizing the benefit of minimal invasiveness of SP flatform, 2) suspicious direct invasion to the rectum, 3) and node-positive disease by preoperative radiologic evaluation. In those cases, tMP-RARP was alternatively performed, including the patients with oligometastatic disease.

Surgical techniques for eSP-RARP and tMP-RARP

For the eSP-RARP, in brief, a 2.5 cm incision was made just below the umbilicus, and then a blind finger dissection was made to the extraperitoneal space between the rectus muscle and the peritoneum behind it (Fig. 1A). The developed extraperitoneal space was extended utilizing a balloon device (Covidien, Minneapolis, MN) under the direct vision of the endoscopy (Fig. 1B). Then, a robotic metal trocar was inserted directly into the skin without applying the floating trocar technique (Fig. 1C). An additional trocar for the assistant and airSeal® device (1.5cm in outer diameter, CONMED, Largo, FL) was inserted on the patient's right side in our eSP-RARP series. For tMP-RARP, four robotic trocars for daVinci X robotic surgical system (Intuitive Surgical, Sunnyvale, CA) were inserted, along with two additional ports for the surgical assistant (5mm and 12 mm in each, Korea) on the right side of the abdomen.

All procedures were performed by a single urologist, who performed over 300 tMP-RARPs during the last ten years before initiating eSP-RARP cases until December 2021. Besides the approach to the prostate and trocar configuration, the surgical techniques for prostatectomy and urethrovesical anastomosis have been maintained since December 2020, when the surgeon applied a modified apical preservation and lateral preserving technique initially introduced by Patel et al [14].

Study design and statistical analysis

The primary endpoint of this study was a comparison of operative time divided by docking time and console time and functional recovery during six months after surgery. The secondary endpoint was the comparison of the functional outcomes in terms of urinary and bowel recovery. Because of the presence of selective criteria for the eSP-RARP group both in size and the clinical stage of PCa from our initial cases, the data for the tMP-RARP group was selected and matched to a 1:1 ratio. Although two surgical options were available after December 2021, tMP-RARP was likely prioritized in patients with a higher-stage disease or cases with the expected procedure difficulty. Therefore, the risk determinants, including baseline PSA, clinical stage by routine radiologic workup, and Gleason grade, as well as the weight of the prostate specimen, were utilized to match the patients between groups.

Given the impact of the so-called learning curve on the peri-operative outcomes, including operative time and functional recovery, the operative time after the matching was compared between groups using the Pearson coefficient. In this study, the docking time was defined as the time between the first incision in the skin and the operator sitting in the console chair after the completion of the robot installation process. The propensity score (PS) matching was performed using a logistic regression model and a caliper width 0.2. Group comparisons were performed using Pearson's chi‐squared test, the Mann–Whitney U test, or Student's t‐test. A p‐value of less than 0.05 was considered statistically significant. The analysis was performed using SPSS Statistics ver. 27.0 (IBM Corperation, Armonk, NY).

The characteristics of the patients before and after PS matching

The mean age of the patient was 69 years old in both groups, and moderate to high-risk PCa occupied the majority of the cases (94% and 96%, respectively). Regarding PCa risk stratification, the tMP-RARP group had significantly higher PSA cutoff and staging criteria than the eSP-RARP group. These differences disappeared after PS matching (Table 1).

The change in operative time and evaluation of the learning curve effect

The operative time trend within all the RARP cases significantly decreased from the initial cases in December 2020 to the last case in December 2022 (Pearson coefficient -.170, p =.037). However, this time-significant reduction in operative time was not seen when limited to the eSP-RARP arm (Pearson coefficient = -.240, p=.093), nor was it seen when the tMP-RARP arm (Pearson coefficient =-.010, p=.923) was examined separately (Fig. 2).

The comparison of peri-operative outcomes and functional recovery after matching

After the PS matching, though the weight of the removed prostate specimen became similar in both groups (27.1 vs. 29.0 g, p=.420), total operative time was significantly faster in eSP-RARP groups than tMP-RARP (149.2 vs. 163.2 minutes, p=.025). Of the operative time, docking time was similar in both groups (15.8±7.8 vs. 15.3±8.1 minutes, p=0.771), and console time was arithmetically shorter in the eSP-RARP group but insignificant (p=0.145, Table 2). The margin positivity, significantly higher in the tMP-RARP group before PS matching, became similar after the matching. In the pT2 stage, the positive margin rate was 14.7 % and 11.7%, respectively (p=.812).

The onset of the liquid diet (1.18 vs. 1.42 days, p=.003), gas-out (1.5 vs. 1.88 days, p=.016), and solid diet (2.26 vs. 3.22 days, p<.001) were significantly faster in the eSP-RARP than in the tMP-RARP group. Single-pad continence was restored within six months in all patients except for one patient in the eSP-RARP arm who had received a spinal cord injury six years before surgery and was on intermittent catheterization pre-and post-operatively. Besides this particular case, the single-pad continence dates (30.5 vs. 51.9 days, p=.145) and zero-pad continence dates (105.5 vs. 146.2 days, p=.210) were similar. The continence status observed at 1, 3, and 6 months post-operatively were also identical between the groups (Table 2).

The daVinci SP is a device designed specifically for the single port procedure. Among the five approaches for radical prostatectomy based on daVinci SP that have been proposed to date [3], we expected its advantages to be maximized in the extraperitoneal approach because it does not pass through the abdominal cavity like the Rezius sparing approach or the conventional transperitoneal approach so that the ileus would be negligible. In Korea, where PCa is primarily found in older men, with the average age of detection being 71 years old [15], a history of previous abdominal surgery is also a factor to consider when using peritoneum. In addition, since the extraperitoneal approach eliminates the need to dissect the bladder like the transvesical or transperitoneal approach, the operation time is expected to be reduced.

As more than half of the PCas detected in Korea are high-risk diseases, most patients in the tMP-RARP group from the historical cohort had different clinical characteristics from the patients included in this study with selection criteria. Therefore, we attempted to correct for the differences between the groups by PS matching. As a result, the differences in initial PSA and stage that existed before PS matching disappeared, and the prostate size and lymph nodal status, which can affect surgical outcomes by influencing the extent of nerve sparing and prolonging operative time, became similar in both groups after exclusion criteria.

A few studies have already reported an extraperitoneal approach using the SP device. In 2020, Kaouk et al. reported the first 10-case series of extraperitoneal approach RARP applying the SP system. The study, which included a mean of 10.1 nodal yield (standard deviation [SD] = 2.6), had an operative time of 197.5 minutes (interquartile range 185.5-229.7 minutes) and achieved complete continence in 50% of patients at 90 days [9]. The first comparison of extraperitoneal versus transperitoneal approaches within an SP platform was reported in 2020 based on the experience of 3 surgeons from 2 different institutions, including 52 cases with eSP-RARP [10]. Operative time was shorter in patients with an extraperitoneal approach (201.0 ± 37.5 vs. 248.2 ± 42.3 minutes, p < 0.00001), where PLND was performed in the majority of cases with eSP-RARP (51/52, median nodal yield of 5), but 90-day social continence rates were similar at 60% and 62.5%, respectively (p = .082). In this series, however, PNLD was performed in only half of the transperitoneal group (24/46 cases), with a significantly higher median nodal yield of 12 than the extraperitoneal counterparts (p < .0001), which makes it difficult to compare the operative time between them. In the most extensive study of patients reported to date, Abou Zeinab et al. compared the outcomes of extraperitoneal and transperitoneal approaches within the SP platform in 650 patients across six hospitals in 2023 [3]. After PS matching, each group was assigned 238 patients with similar preoperative characteristics. Reversely, the operative time from this series was significantly longer in the extraperitoneal approach group (206 vs. 155 minutes, p < .001) at the cost of a higher PLND rate (84.5% vs. 52.9%, p < .001), but the length of stay was shorter. Incontinence rates, defined as using up to one pad, did not differ between the groups (90-day continence rate = 53.0% vs 63.09%, p = .051). On the other hand, in the present study focusing only on the RARP procedure recruiting cases that omitted the need for PNLD, the operative time was shorter in the eSP-RARP group than in these previous reports, with a mean of 149. 2 (± 22.8 minutes [SD], mean console time of 107 minutes) minutes in the eSP-RARP group and 163.2 (± 37.0 minutes, mean console time of 112 minutes) minutes in the tMP-RARP group, which is also shorter than previous reports but significantly extended than eSP-RARP. The present study's 90-day single-pad continence rate of 92% vs. 82% (52% vs. 56% in zero-pad) was also notable.

In general, multicenter studies can be considered more reliable than single-center studies. Still, when introducing new surgical modalities that may affect surgical outcomes, each operator is bound to have different surgical volumes, workloads, surgical principles, and patient selection criteria, all of which affect the RARP performance. Therefore, a single-operator study may be the best way to distinguish the differences if everything other than the surgical instrument is constant. However, even in this case, if the timing of the predominant use of each surgical device is different, it is possible that the eSP-RARP group, which was predominantly operated on at the end of the time series, may appear to have improved operative time and performance as the so-called learning curve is overcome. If the overall operating time decreased, it is necessary to distinguish whether it was due to the conversion of the surgical instrument or the learning curve effect within each surgical method. As a result, as shown in Fig. 2, although no statistically significant difference was observed in each surgical procedure itself, it was statistically confirmed that the overall surgical time decreased during eSP-RARP compared to tMP-RARP. Therefore, the reduction in operating time seems primarily due to the conversion of surgical instruments and approach methods. In particular, it is noteworthy that the extraperitoneal approach took the same docking time as the transperitoneal multi-port approach using the SP device (15.3 ± 8.1 vs. 15.4 ± 9.6 minutes, p = .771 before PS matching), reflecting that the reduction in operative time was mainly in the area of console time.

The authors acknowledge the limitations of this retrospective, single-center study. The cost difference with tMP-RARP must be considered in any cost-effectiveness comparison. Due to the limitations of the Korean health insurance system, it is difficult to calculate and compare the costs used accurately. However, eSP-RARP in this study was performed using only a metal trocar without applying the floating trocar technique, as depicted in Figs. 1A-C. This was an attempt to maximize minimal invasiveness, as a prostate weighing less than 50 g could be easily extracted extracorporeally with only a 2.5 cm incision, as well as to minimize costs by using only the simplest type of trocar. In the future, with the development of technology, surgery using SP devices will be able to overcome the previous technical hurdles and replace multi-port procedures more quickly, and further prospective studies are expected to show its actual advantages.

daVinci SP-based RARP restored bowel function faster with shorter operative time through an extraperitoneal approach than the conventional transperitoneal multi-port counterpart while maintaining similar incontinence outcomes in cases without a routine PNLD, even applying the same surgical techniques.

Acknowledgment

None

Author contribution:

Conceptualization: YHK

Data curation: YHK, JYJ

Formal analysis: SWK

Funding acquisition: YHK

Investigation: YUK

Methodology: JYJ

Project administration: YHK

Resources: YHK

Software: SWK

Supervision: YHK

Validation: SWK, YUK

Visualization: YHK

Writing – original draft: YHK

Writing – review & editing: YHK, SWK

Author’s disclosure

The authors have no conflict of interest in this article.

Funding

This work was supported by the Yeungnam University Research Fund (2023)

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Table 1. The summary of prostate cancer risk-stratification between groups, before and after propensity matching.

	Extraperitoneal SP-RARP (N=50)	Transperitoneal MP-RARP, Before PS matching (N=100)	p-value, Before PS matching	Transperitoneal MP-RARP, After 1:1 matching (N=50)	p-value, After PS matching
Age (year)	69.8±6.0	69.0±6.3	.468	68.7±5.4	.342
55-69	25 (50%)	55 (55%)	.563	29 (58%)	.547
≥70	25 (50%)	45 (45%)		21 (42%)
Initial PSA (ng/mL)	11.25±10.3	46.5±117.6	.036	60.8±160.1	.031
<10	34 (68%)	45 (45%)	.011	26 (52%)	.083
10-19	10 (20%)	22 (22%)		9 (18%)
≥20	6 (12%)	33 (33%)		15 (30%)
Pathologic Stage
≤ pT2	34 (68%)	47 (47%)	.015	34 (68%)	.832
≥ pT3	16 (32%)	53 (53%)		16 (32%)
Seminal vesicle invasion (%)	4 (8%)	21 (21%)	.044	5 (10%)	.727
Gleason Score
6	6 (12%)	9 (9%)	.448	7 (14%)	.955
7	35 (70%)	64 (64%)		34 (68%)
8-10	9 (18%)	27 (27%)		9 (18%)
NCCN risk-stratification			.109		.918
Low ≤	3 (6%)	4 (4%)		3 (6%)
Intermediate	24 (48%)	32 (32%)		22 (44%)
≥ High	23 (46%)	64 (64%)		25 (50%)

Table 2. The summary of peri-operative outcomes between groups, before and after propensity matching.

	Extraperitoneal SP-RARP (N=50)	Transperitoneal MP-RARP, Before PS matching (N=100)	p-value, Before PS matching	Transperitoneal MP-RARP, After 1:1 matching (N=50)	p-value, After PS matching
Removed prostate weight (g)	27.1±8.5	28.1±10.9	.575	29.0±13.8	.420
Total operative time (minutes)	149.2±22.8	165.5±38.2	.006	163.2±37.0	.025
for Docking	15.8±7.8	15.4±9.6	.776	15.3±8.1	.771
for Console	107.0±24.6	114.1±29.8	.145	112.3±28.8	.322
Margin positive (%)	12 (24%)	58 (58%)	<.001	11 (22%)	.812
≤ pT2	5 (14.7%, 5/34)	17 (36.2%. 17/47)		4 (11.7%, 4/34)
≥ pT3	7 (43.7%, 7/16)	23 (43.4%, 23/43)		7 (43.7%, 7/16)
Date of gas out (POD)	1.50±0.61	1.98±0.65	<.001	1.88±0.62	.003
Date of liquid diet (POD)	1.18±0.38	1.54±0.64	<.001	1.42±0.57	.016
Date of solid diet (POD)	2.26±0.48	3.25±0.67	<.001	3.22±0.61	<.001
Date of catheter removal (POD)
Date of discharge (POD)	6.30±0.90	6.98±2.35	.012	6.72±1.03	.033
Date of 1-pad continence (POD)	30.5±34.7 (100%)	65.2±121.4 (99%)	.009	51.9±95.7 (98%)	.145
1-pad continence at 30 days	35 (70%)	59 (59%)	.213	31 (62%)	.527
1-pad continence at 90 days	46 (92%)	82 (82%)	.142	41 (82%)	.234
1-pad continence at 180 days	49 (98%)	90 (90%)	.101	46 (92%)	.362
Date of 0-pad continence (POD)	105.5±90.0 (94%)	146.9±196.4 (93%)	.090	146.2±201.6 (94%)	.210
0-pad continence at 30 days	10 (20%)	19 (19%)	.884	14 (28%)	.483
0-pad continence at 90 days	26 (52%)	53 (53%)	.908	28 (56%)	.841
0-pad continence at 180 days	38 (74%)	70 (70%)	.703	36 (72%)	.824

No competing interests reported.

Faster both in operative time and functional recovery by the extraperitoneal daVinci SP- based robot-assisted radical prostatectomy: A propensity score matching analysis compared to transperitoneal multiport counterpart

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Journal Publication

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Abstract

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Introduction

Methods

Results

Discussion

Conclusion

Declarations

References

Tables

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Status:

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