Comparison of robotic-assisted laparoscopic radical prostatectomy: SP versus XI, a single surgeon experience

Currently, there is a paucity of data regarding Single Port (SP) robotic-assisted laparoscopic prostatectomy (RALP). Our objective was to compare our single-institution single-surgeon SP RALP experience to our XI RALP experience with regard to patient selection, perioperative data, and outcomes. Patients who underwent prostatectomy at our institution between August 2019 and April 2021 were selected for analysis. All patients had biopsy confirmed prostate cancer. All surgeries were performed by one urologist at our institution to limit inter-surgeon variability. Demographic and clinical information were extracted from the medical record in standardized fashion. All documented classifications were graded using the Clavien–Dindo classification system. Patients with previous prostate cancer therapies were excluded. Categorical variables were compared using Chi-square or Fisher’s exact test where appropriate. Continuous variables were compared using t tests or Wilcoxon rank sum tests where appropriate. Complete records were available for 208 patients. Of the total patient population 127 (61.1%) underwent SP prostatectomy compared to 81 (38.9%) underwent XI prostatectomy. There was no significant difference between the two cohorts in terms of mean age (65 vs. 66 years; p = 0.60), BMI (29.2 vs. 30.1; p = 0.22), preop ASA score ≥ 3 (68.5% vs. 64.2%; p = 0.52), or preop PSA (7.1 vs. 7.4, p = 0.94). There no difference in procedure time for SP prostatectomy (170 vs. 168 min, p = 0.035), estimated blood loss (100 vs. 100 mL; p = 0.14), or average length of stay (1 vs. 1 days; p = 0.22). There was a significant difference in Gleason grade group between the two cohorts with patients undergoing XI RALRP more likely to have higher stage disease (p = 0.025) and a trend towards higher D’Amico risk scores in the XI group (p = 0.053). There was no difference in rate of positive surgical margins (29.9% vs. 29.6%; p = 0.96). There was no difference in the distribution of complications between the two groups (p = 0.99) with 89% of patients having no complication. There was no difference in the number of lymph nodes removed by modality (p = 0.94). To date, this study represents one of the largest cohorts of patients who underwent SP RALP. Importantly, it is among the first studies comparing perioperative variables between the SP and XI platforms. As surgeons become more facile with the SP system there appear to minimal differences in patient factors, perioperative results, or outcomes between the platforms. These findings provide evidence that surgeons who are competent on the XI platform can confidently perform SP RALPs through a single incision without compromising outcomes.


Introduction
Robotic-assisted laparoscopic radical prostatectomy (RALRP) is the current standard for the treatment of clinically significant prostate cancer (CSPCa).The minimally invasive approach offers patients excellent results with respect to postoperative recovery and cosmesis while granting the surgeon increased dexterity and visualization [1].Currently, the DaVinci surgical system (Intuitive Surgical; Sunnyvale, CA) is the leading platform for robotic urologic surgery and is FDA-approved since the early 2000s.Robotic surgery confers increased benefits in reducing morbidity and improving patient satisfaction, but is associated with a significant level of investment both in the purchasing and regular maintenance of the system in its life cycle [2].Furthermore, with each iteration of the technology, there exists a need for a head-to-head comparison with older models to determine any added value for patients, physicians, and hospital systems.If a new platform cannot be proven to provide at least as good of outcomes as an older generation, then its widespread adoption should not occur.In 2018, a model now known as the Davinci Single-Port (SP) received FDA approval for urologic procedures [3].The SP system relies on just a single surgical incision to deliver multiple articulating tools into the body.Initial case reports from small series have deemed the DaVinci SP to show promise in terms of safety and efficacy [4].However, there is currently a paucity of data directly comparing RALRP outcomes between the SP system and its predecessor, the DaVinci Xi.Our objective was to analyze SP RALRP outcomes and compare them to Xi outcomes at a single tertiary care academic medical center using a single-surgeon control to avoid possible intersurgeon bias.

Methods
All patients had biopsy confirmed CSPCa, defined as Gleason grade group 2 or higher.All underwent RALRP with curative intent.All surgeries were performed by a single surgeon (AS) at a tertiary care academic center in the United States.The cohort included 127 consecutive SP cases performed from December 2018 to April 2021, which represents the time frame from which the SP platform began being used at our institution for RALRP.Likewise, 81 consecutive XI cases from March 2018 to April 2021 were selected for comparison.The dates of the comparison XI cohort were selected to compare a contemporaneous cohort of XI RALRP patients to obtain a real-world comparison given the widespread adoption of the XI platform.Patients with previous prostate cancer therapies were excluded (e.g., brachytherapy, radiation, cryoablation).Patients were not randomized to robotic platform, rather patient selection was decided by the surgeon based on factors such as prostate size, suspicion of potential extensive lysis of adhesions, and those with specific comorbidities (e.g., large ventral hernia).In addition, to facilitate appropriate comparison, all procedures were done via a transperitoneal approach.For the SP system, we utilized an assistant port with an AirSeal in addition to the standard SP port.No gelport was used.Preoperative patient variables included mean age, race, average BMI, PSA, ISUP Gleason grade group, ASA score dichotomized as ≤ 2 or ≥ 3, and prostate volume (as assessed on preoperative prostate MRI or CT where MRI unavailable).Perioperative outcomes of interest included procedure time, length of stay, final estimated blood loss (EBL), length of stay (LOS), incidence of complications and histopathologic data.Procedure time was recorded as time from incision to completion of closure.Complications were assessed with the Clavien-Dindo classification system [5].Histopathological data included grade group, tumor stage, positive surgical margins, and node yield.All pathology slides were reviewed by the same pathologist who specializes in GU pathology.Variables were analyzed using STATA statistical software, version 16 (StataCorp.2019 College Station, TX).Chisquare, Fisher's exact test, paired t tests, and Wilcoxon rank sum tests were used where appropriate.

Discussion
Robotic surgery for urologic conditions continues to evolve at a rapid rate with advancements focusing on primarily reducing morbidity.The newest iteration of the surgical system being adopted alongside the standard XI multi-port platform is the SP robot.The SP has its advantages in a single surgical docking arm and single laparoscopic trocar through which the camera and instruments articulate.With a shared paradigm of offering patients the most minimally invasive approach to treat their cancer, several centers have begun reporting their initial experiences for RALRP with the DaVinci SP.To drive more widespread adoption of the next generation of a system that already produces excellent outcomes, there must be a strong argument favoring its value added.Lenfant et al. performed a cost comparison between the SP and Xi systems and demonstrated economic viability of the SP robot for RALRP, showing that although the cost for surgical consumables was higher for the SP cases, this was offset by lower cost from reduced hospital stay [6].Importantly, many centers have reported favorable outcomes in their initial experience of SP RALRP in a limited series of cases [7][8][9][10][11].These authors report similar ranges of procedures times, hospital stay, and incidence of complications to those that we report.However, this is one of the first reports of perioperative outcomes between the SP and Xi RALRP performed by a single surgeon.The retrospective study design precludes randomization, therefore, includes both measured and unmeasured confounding.Decision on which platform to use for each case was made by the primary surgeon.We attempted to control for this as best as possible by only including results from a single surgeon at our highvolume center.In addition, we included contemporaneous cohorts to avoid possible confounding from evolving management of prostate cancer over time.Our analysis showed no difference in procedure time, EBL, node count, margin status, Clavien complications or length of stay.This provides more evidence to a growing body of literature that SP RALRP is comparable to XI RALRP in terms of short-term postoperative outcomes.Combined, these data show that SP RALRP is not only accessible to urologists competent on the XI system, but that perioperative and pathologic outcomes are the same.In our experience we found that factors that allowed for similar outcomes included use of the same staff for cases, awareness of the strengths and limitations of the SP platform, and use of the assistant port for SP cases.For example, the diminished grip strength on the SP platform was our rationale for preferentially performing RALRPs on larger prostates with the Xi system, and patient's with suspected extensive multi-quadrant intraabdominal adhesions were preferentially performed on the SP system given the enhanced rotational capabilities of the SP platform.Knowledge of these strengths and limitations can enhance patient selection to allow for optimal outcomes.Our study does have some limitations, however.For instance, we did not compare pain scores between the two cohorts.Vigneswaran et al. showed that patients undergoing SP RALRP had decreased pain on postoperative day 1 [7].Similarly, Noël et al. reported higher scores on the Surgical Satisfaction Questionnaire (SSQ-8) in patients who underwent SP prostatectomy than those who underwent surgery with the Xi system [12].Although both groups had high satisfaction scores overall, a main contributor to better satisfaction in the SP group was the better pain control and decreased number of surgical scars.We also did not stratify between intraperitoneal vs. extraperitoneal, and nerve sparing vs. non-nerve sparing.Although the vast majority of the RALRPs that performed at our center are intraperitoneal and nerve sparing, further head-to-head investigation is needed as others have reported on the safety and efficacy of extraperitoneal SP RALRP [13].In addition, our lymph node yield was somewhat lower than other reports, though evidence suggests that higher lymph node yields during RALRP are not impactful on rate of biochemical recurrence [14].While there are a select number of reports [15], further research is also needed to better characterize the learning curve of the SP platform that is present with any new surgical technique.In the future, we hope to analyze and compare long term functional outcomes such as urinary incontinence and erectile dysfunction between the two systems.

Conclusions
We conducted one of the largest studies to date comparing perioperative variables for robotic-assisted laparoscopic prostatectomy performed by a single surgeon on the DaVinci SP and Xi platforms.There were no statistically significant differences seen between perioperative or pathological outcomes between the two groups.Likewise, there were no differences in complications between the two groups.Furthermore, as a function of time, there was not a meaningful trend seen in SP operative variables.These findings provide evidence that surgeons who are competent on the XI platform can confidently perform SP RALRPs through a single incision without compromising patient outcomes.

Table 1
Graph of operative time for RALP between SP and XI platform