Development of Patient-Specific Nomogram to Assist in Clinical Decision-Making for Single Port Versus Multi-Port Robotic Partial Nephrectomy: A Report from the Single Port Advanced Robotic Consortium

Abstract

Objective:

To develop a patient-specific algorithm to better guide clinical decision-making when considering between single port (SP) and multi-port (MP) robotic partial nephrectomy (RPN).

Materials and Methods:

A retrospective review was performed on the institutional review board–approved, prospectively maintained multi-institutional database of the Single Port Advanced Research Consortium to identify all consecutive patients who underwent SP and MP-RPN between 2019 and 2023. Baseline clinicodemographic variables were used to identify the significant predictors of SP-RPN. The significant variables were used to construct a nomogram to predict the likelihood of SP vs MP-RPN.

Results:

Of the 1021 patients included in our analysis, 189 (18.5%) and 832 (81.5%) underwent SP and MP-RPN, respectively. Statistically significant predictors of SP-RPN included a lower comorbidity profile, a significant abdominal surgical history as characterized by a higher Hostile Abdomen Index, as well as tumors of lower complexity. The nomogram generated using the aforementioned variables demonstrated a reasonable performance with an area under the curve of 0.79. An optimal cutoff point was determined, with likelihood ratios above 0.12 indicating a preference for SP-RPN. Of note, all SP-RPN cases that scored above the 0.12 cutoff exhibited improved perioperative outcomes, including shorter ischemia time and less intraoperative blood loss.

Conclusions:

In this study, we have devised a novel patient selection nomogram aimed at enhancing clinical decision-making within the expanding repertoire of RPN approaches. The findings highlighted in this study offer valuable guidance to facilitate appropriate patient selection and thereby ensuring favorable perioperative outcomes associated with RPN procedures.

Introduction

For many years, nephron-sparing surgery has been considered the gold standard for the management of localized small renal masses. The hallmark of partial nephrectomy included the achievement of negative surgical margins and satisfactory oncological outcomes while ensuring minimal perioperative morbidity and optimal renal function preservation. The utility of robotic surgical platforms for partial nephrectomy has been previously demonstrated, with significant advancements in visualization and ergonomics allowing for improved perioperative outcomes and for partial nephrectomy to be completed in renal tumors of higher complexity.^1
–3

The subsequent introduction of the purpose-built single-port (SP) robotic platform (Intuitive Surgical, Sunnyvale, CA) opened a new frontier within the domains of minimally invasive surgery.^4,5 The distinctive features of the novel platform included the narrow profile of the single robotic arm that can simultaneously accommodate one flexible, three-dimensional, high-definition endoscopic camera and three double-jointed robotic instruments. Together with the capabilities for floating-docking technique, as facilitated by the purpose-built SP Access Kit (Intuitive Surgical, Sunnyvale, CA), the SP provided further improvements in ergonomics, maneuverability, and precision, especially when performing procedures in smaller and shallow surgical working spaces from a single anatomical pivot point.⁶

Although the utility of the SP platform for different approaches of robotic partial nephrectomy (RPN) has been previously demonstrated, including transperitoneal and retroperitoneal techniques,^7,8 recent advancements, such as the low anterior access (LAA) incision, have further pushed the boundary favoring further improvement in postoperative recovery and patient comfort.^9,10 Appreciating the expanding repertoire of RPN approaches and the varying benefits offered by the different techniques, this study sought to address the growing need for an evidence-based, patient-specific algorithm to guide clinical decision-making between SP and multi-port (MP) RPN, with emphasis on the comparative effectiveness and outcomes of these approaches in nephron-sparing surgery.

Materials and Methods

A retrospective review was performed on the prospectively maintained database of the Single-Port Advanced Research Consortium (SPARC) to identify all consecutive patients who underwent RPN between 2019 and 2023. The consortium is a growing multi-institutional collaboration, currently involving 21 institutions that perform SP urological procedures within the United States. All participating centers are required to have their respective institutional review board approval and data-sharing agreements with the host institution. The SPARC kidney database contained information from 14 surgeons across 10 different institutions. Given most of the surgeons in this study began performing SP surgery in 2019, and the primary objective of this study was to compare the baseline clinicodemographic characteristics of the patients who underwent SP and MP-RPN, we have only included MP cases performed from 2019 to 2023.

All procedures were performed by experienced robotic surgeons using the da Vinci Xi or SP robotic surgical systems (Intuitive Surgical, Sunnyvale, CA) with either transperitoneal or retroperitoneal techniques that have been described previously.^5,7,11 For all cases of SP-RPN, all robotic instruments, flexible endoscopic camera, as well as the flexible Remotely Operated Suction Irrigation system (Vascular Technology Inc., Nashua, NH) were inserted through the multichannel cannula of the SP Access Kit, which was placed through a single 3.5-cm incision. At our institution, SP-RPN was routinely performed via a retroperitoneal approach using the LAA incision. In this approach, a single incision was made at two fingers breadth above the superior pubic ramus on the ipsilateral side. Blunt dissection using the surgeon’s finger was then performed to gently sweep the peritoneum and to open the space for the placement of the SP Access Kit (Fig. 1). After robot docking and upon entry into the retroperitoneum, the psoas major muscle can be immediately visualized and used as the anatomical landmark to continue dissections proximally toward the kidney. The placement of an additional port or use of a surgical drain tube is typically not indicated but such decision remains at the discretion of the individual surgeons.

FIG. 1.

Comparison of single-port (SP) low anterior access (LAA) retroperitoneal approach and multi-port (MP) transperitoneal technique for robotic partial nephrectomy (RPN).

Baseline clinicodemographic variables considered in our analysis include age, ethnicity, body mass index (BMI), comorbidities according to the American Society of Anesthesiologist (ASA) score and Charlson Comorbidity Index (CCI), history of abdominal surgery, preoperative renal function, as well as the tumor size, location, and characteristics according to the RENAL Nephrometry Score.¹² The Hostile Abdomen Index (HAI) was applied in this study to better categorize the extent of the patient’s history of abdominal surgery (Supplementary Table S1).¹³ Preoperative renal function was reported as the estimated glomerular filtration rate (eGFR) and the baseline chronic kidney disease (CKD) stages according to the National Kidney Foundation Kidney Disease Outcome Quality Initiatives.

For the purpose of this study, several perioperative variables were collected to determine the success of the respective procedures. Intraoperative parameters collected in this study included operative time, warm ischemia time, estimated intraoperative blood loss, and any evidence of intraoperative complication. Other perioperative outcomes included surgical margin status, length of postoperative hospital stay, evidence of postoperative complication, as well as postoperative renal function. Postoperative complication was reported in accordance with the Clavien–Dindo classification with major complications defined as those scoring 3a and above.¹⁴ In addition to the eGFR, postoperative renal function was also reported as the percent eGFR preservation compared with the baseline renal function. Clinically significant CKD upstaging was defined as any CKD progression from Stage 1 (≥90 mL/min/1.73m²) or 2 (60–89 mL/min/1.73m²) to Stages 3a (45–59 mL/min/1.73m²) or above, from Stage 3a to 3b (30–44 mL/min/1.73m²) or above, from Stage 3b to 4 (15–29 mL/min/1.73m²) or above, or from Stage 4 to 5 (<15 mL/min/1.73m²).

Statistical analysis was performed using RStudio version 12.0 (R Packages for Statistical Computing, Vienna, Austria) with categorical variables presented as the absolute and relative percent frequencies, while continuous variables were presented as the median and interquartile range. Univariate and multivariate regression analyses were performed with a p-value of <0.05 considered statistically significant. All of the statistically significant baseline predictors of SP vs MP-RPN were subsequently identified and incorporated to construct our nomogram. A receiver operating characteristics curve was generated to evaluate the area under the curves (AUC) and to determine the predictive performance of the nomogram. Additionally, the optimal cutoff point of the likelihood ratio that maximized the overall performance of the tests in terms of maximizing sensitivity and specificity was calculated.

Results

A total of 1021 patients were included in our analysis, which comprised 189 (18.5%) SP and 832 (81.5%) MP-RPN cases. A summary of the baseline demographic and clinical characteristics of the two groups was described in Table 1. All SP cases were completed without the need for conversion. Of note, although the SP cohort was found to be younger (median age, SP 60 vs MP 62 years, p < 0.05) and with fewer comorbidities (median CCI, SP 3 vs MP 4, p < 0.001), the group was associated with a significantly higher prevalence of hostile abdomen (HAI 4, SP 6.8% vs MP 3.9%, p < 0.05). In terms of the baseline tumor characteristics, patients referred for SP typically had a lower RENAL Nephrometry Score (median, SP 5 vs MP 7, p < 0.001), most of which were influenced by the smaller size, exophytic nature, and the location of the tumor being entirely above or below the renal polar lines. Other preoperative variables, including the baseline renal function, remained similar between the two groups.

Table 1.

Baseline Clinicodemographic Variables of All Included Patients, as Categorized Based on the Patients Who Underwent Multi-Port and Single-Port Robotic Partial Nephrectomy

	Overall cohort	Multi-port	Single-port	p
n (%)	1021	832 (81.5%)	189 (18.5%)
Age (years), median (IQR)	62 (54–69)	62 (54–70)	60 (52–68)	<0.05
Gender (male), n (%)	627 (61.5%)	524 (63.1%)	103 (54.8%)	<0.05
Ethnicity				<0.001
African American, n (%)	115 (12%)	84 (10.8%)	31 (17.7%)
Asian/Pacific Islander, n (%)	39 (4.1%)	26 (3.3%)	13 (7.4%)
Caucasian, n (%)	662 (69.3%)	590 (75.6%)	72 (41.1%)
Hispanic, n (%)	113 (11.8%)	62 (7.9%)	51 (29.1%)
Other ethnicity, n (%)	26 (2.7%)	18 (2.3%)	8 (4.6%)
BMI (kg/m²), median (IQR)	29.2 (25.7–34.1)	29.4 (25.9–34.3)	28.1 (24.7–32.1)	<0.05
ASA Score				<0.001
ASA 1–2, n (%)	340 (37.5%)	259 (34.1%)	81 (55.1%)
ASA 3–4, n (%)	567 (62.5%)	501 (65.9%)	66 (44.9%)
CCI, median (IQR)	3 (2–5)	4 (2–5)	3 (2–4)	0.076
Previous abdominal surgery (HAI)				<0.05
HAI 1, n (%)	533 (56.6%)	464 (58.3%)	69 (47.3%)
HAI 2, n (%)	244 (25.9%)	197 (24.7%)	47 (32.2%)
HAI 3, n (%)	124 (13.2%)	104 (13.1%)	20 (13.7%)
HAI 4, n (%)	41 (4.4%)	31 (3.9%)	10 (6.8%)
Baseline GFR (mL/min/1.73m²), median (IQR)	83.3 (66.3–98)	82.5 (65.6–97.8)	86.1 (70.6–98.1)	0.887
Baseline CKD stage				0.214
CKD stage 1, n (%)	366 (38.9%)	301 (38%)	65 (43.9%)
CKD stage 2, n (%)	406 (43.1%)	344 (43.4%)	62 (41.9%)
CKD stage 3a, n (%)	112 (11.9%)	99 (12.5%)	13 (8.8%)
CKD stage 3b, n (%)	43 (4.6%)	38 (4.8%)	5 (3.4%)
CKD stage 4, n (%)	11 (1.2%)	9 (1.1%)	2 (1.4%)
CKD stage 5, n (%)	3 (0.3%)	2 (0.3%)	1 (0.7%)
Laterality (right), n (%)	509 (50.1%)	418 (50.5%)	91 (48.7%)	0.721
Hilar tumor, n (%)	153 (17.8%)	135 (18%)	18 (16.5%)	0.816
Largest tumor diameter (cm), median (IQR)	3.1 (2.3–4.4)	3.2 (2.4–4.5)	2.5 (2–3.5)	0.072
Tumor diameter				<0.05
≤4 cm, n (%)	539 (70.8%)	431 (68.2%)	108 (83.7%)
>4 cm and ≤7 cm, n (%)	189 (24.8%)	172 (27.2%)	17 (13.2%)
>7 cm, n (%)	33 (4.3%)	29 (4.6%)	4 (3.1%)
Exophytic/Endophytic				<0.001
≥50% exophytic, n (%)	326 (44.2%)	259 (41.6%)	67 (58.8%)
<50% exophytic, n (%)	319 (43.3%)	276 (44.3%)	43 (37.7%)
Completely endophytic, n (%)	92 (12.5%)	88 (14.1%)	4 (3.5%)
Nearness to collecting system				0.075
≥7 mm, n (%)	246 (33.5%)	198 (31.8%)	48 (42.5%)
>4 mm and <7 mm, n (%)	239 (32.5%)	205 (33%)	34 (30.1%)
≤4 mm, n (%)	250 (34%)	219 (35.2%)	31 (27.4%)
Anterior/Posterior				0.612
Anterior, n (%)	254 (27.8%)	207 (27.3%)	47 (29.9%)
Posterior, n (%)	399 (43.7%)	329 (43.5%)	70 (44.6%)
Neither, n (%)	261 (28.6%)	221 (29.2%)	40 (25.5%)
Tumor location relative to polar lines				<0.001
Entirely above or below, n (%)	338 (45.9%)	254 (40.8%)	84 (73.7%)
Crosses a polar line, n (%)	270 (36.7%)	254 (40.8%)	16 (14%)
>50% across polar line, or crosses axial renal midline, or entirely between polar lines, n (%)	128 (17.4%)	114 (18.3%)	14 (12.3%)
RENAL score	6 (5–8)	7 (5–8)	5 (4–7)	<0.001
Low complexity (4–6), n (%)	370 (48.6%)	292 (46.1%)	78 (60.5%)
Intermediate complexity (7–9), n (%)	305 (40%)	269 (42.5%)	36 (27.9%)
High complexity (10–12), n (%)	61 (8%)	61 (9.6%)	0 (0%)
Clinical T (cT) stage				<0.05
cT1a, n (%)	494 (68.7%)	419 (66.3%)	75 (86.2%)
cT1b, n (%)	162 (22.5%)	154 (24.4%)	8 (9.2%)
cT2a, n (%)	17 (2.4%)	15 (2.4%)	2 (2.3%)
cT2b, n (%)	3 (0.4%)	1 (0.2%)	2 (2.3%)
cT3a, n (%)	41 (5.7%)	41 (6.5%)	0 (0%)
cT3b, n (%)	1 (0.1%)	1 (0.2%)	0 (0%)
cT4, n (%)	1 (0.1%)	1 (0.2%)	0 (0%)

Baseline CKD stage was defined in according to the National Kidney Foundation (NKF) Kidney Disease Outcomes Quality Initiatives (KDOQI) with CKD 1 = ≥ 90 mL/min/1.72 m²; CKD 2 = 60–89 mL/min/1.72 m²; CKD 3a = 45–59 mL/min/1.72 m²; CKD 3b = 30–44 mL/min/1.72 m²; CKD 4 = 15–29 mL/min/1.72 m²; and CKD 5 = <15 mL/min/1.72 m².

ASA = American Society of Anesthesiologist; BMI = body mass index; CCI = Charlson Comorbidity Index; CKD = chronic kidney disease; HAI = Hostile Abdomen Index, with 0 referring to the absence of previous abdominal surgery and 4 being indicative of hostile abdomen with multiple previous abdominal surgeries; IQR = interquartile range; GFR = glomerular filtration rate.

On univariate regression analysis, several preoperative variables were identified as independent predictors of SP-RPN. These included younger age, male gender, lower BMI, lower ASA score, and a higher HAI. Furthermore, with lower RENAL scores also identified as an independent predictor of SP-RPN, smaller tumor diameter, exophytic tumor, increased distance between the tumor and the collecting system, as well as the location of the tumor relative to the renal polar lines were also found to be statistically significant. Despite these differences, subsequent multivariate analysis identified a lower ASA score (odds ratio [OR] −1.102, 95% confidence interval [CI] −1.713 to −0.517, p < 0.05), a more significant abdominal surgical history (HAI, OR 0.421, 95% CI 0.093–0.743, p < 0.05), a smaller tumor diameter (OR −0.121, 95% CI −0.338 to −0.001, p < 0.05), a more exophytic tumor (OR −0.521, 95% CI −1.031 to −0.045, p < 0.05), and tumors located entirely above or below the polar lines (OR −0.785, 95% CI −1.345 to −0.281, p < 0.05) to be significant predictors of SP-RPN (Table 2). All five variables were then used to construct the nomogram as presented in Figure 2 with an example of the clinical application provided in Supplementary Figure S1. Subsequent evaluation of the predictive nomogram demonstrated a reasonable performance with an AUC of 0.79 (Fig. 3).

FIG. 2.

Nomogram predicting the likelihood of single-port (SP) compared with multi-port (MP) robotic partial nephrectomy (RPN) based on the statistically significant baseline clinicodemographic variables identified on multivariate regression analysis.

FIG. 3.

Receiving operator characteristics (ROC) for the logistic regression model that predicted the likelihood of single-port (SP) compared with multi-port (MP) robotic partial nephrectomy (RPN), along with the area under the curve (AUC) and the optimal cutoff point of the likelihood ratio that maximized the overall performance of the tests in terms of maximizing sensitivity and specificity.

Table 2.

Univariate and Multivariate Regression Analyses Evaluating the Likelihood of Single-Port vs Multi-Port Robotic Partial Nephrectomy Based on the Baseline Clinicodemographic Characteristics

	Univariate			Multivariate
	OR	95% CI	p	OR	95% CI	p
Age	−0.015	−0.028 to −0.002	<0.05	−0.024	−0.048 to 0.001	0.052
Gender	0.343	0.021 to 0.662	<0.05	0.323	−0.260 to 0.903	0.274
Ethnicity	0.107	−0.085 to 0.205	0.282
BMI	−0.037	−0.066 to −0.009	<0.05	−0.021	−0.070 to 0.026	0.402
ASA score	−0.886	−1.210 to −0.567	<0.001	−1.102	−1.713 to −0.517	<0.05
CCI	−0.083	−0.177 to 0.007	0.076
Previous abdominal surgery (HAI)	0.219	0.024 to 0.408	<0.05	0.421	0.093 to 0.743	<0.05
Preoperative GFR	−0.001	−0.006 to 0.002	0.887
Baseline CKD stage	−0.129	−0.338 to 0.069	0.214
Laterality	0.056	−0.258 to 0.373	0.721
Hilar tumor	−0.101	−0.668 to 0.416	0.714
Largest tumor diameter	−0.671	−1.118 to −0.267	<0.05	−0.121	−0.338 to −0.001	<0.05
≤4 cm	0.875	0.398 to 1.395	<0.001
>4 cm and ≤7 cm	−0.912	−1.473 to −0.388	<0.05
>7 cm	−0.407	−1.636 to 0.547	0.453
Exophytic/Endophytic	−0.665	−1.006 to −0.342	<0.001	−0.521	−1.031 to −0.045	<0.05
≥50% exophytic	0.695	0.292 to 0.105	<0.001
<50% exophytic	−0.273	−0.689 to 0.134	0.193
Completely endophytic	−1.509	−2.710 to −0.609	<0.05
Nearness to collecting system	−0.275	−0.525 to −0.030	<0.05	−0.337	−0.707 to 0.022	0.069
≥7 mm	0.458	0.045 to 0.866	<0.05
>4 mm and <7 mm	−0.133	−0.579 to 0.295	0.549
≤4 mm	−0.363	−0.820 to 0.072	0.110
Anterior/Posterior	−0.021	−0.227 to 0.187	0.840
Location relative to polar lines	−0.834	−1.180 to −0.520	<0.001	−0.785	−1.345 to −0.281	<0.05
Entirely above or below	1.400	0.965 to 1.860	<0.001
Crosses a polar line	−1.442	−2.028 to −0.917	<0.001
>50% across polar line, or Crosses axial renal midline, or Entirely between polar lines	−0.472	−1.106 to 0.093	0.120
RENAL score	−0.322	−0.421 to −0.227	<0.001
Low complexity (4–6)	0.580	0.197 to 0.970	<0.05
Intermediate complexity (7–9)	−0.647	−1.073 to −0.239	<0.05
High complexity (10–12)	−1.608	−2.947 to 3.427	0.975

Baseline CKD stage was defined in according to the NKF KDOQI with CKD 1 = ≥ 90 mL/min/1.72 m²; CKD 2 = 60–89 mL/min/1.72 m²; CKD 3a = 45–59 mL/min/1.72 m²; CKD 3b = 30–44 mL/min/1.72 m²; CKD 4 = 15–29 mL/min/1.72 m²; and CKD 5 = <15 mL/min/1.72 m².

CI = confidence interval; OR = odds ratio.

To evaluate the clinical benefits of our nomogram, we proceeded to compare the perioperative outcomes of the SP-RPN cases who scored above or below the calculated optimal probability threshold of 0.12. After applying our nomogram for the 189 included SP-RPN cases, 54 (28%) were found to score above the likelihood ratio of 0.12, whereas the remaining 135 (72%) scored below the cutoff. The cases who scored above the cutoff were found to have significantly shorter ischemia time (median, above 11 vs below 19 minutes, p < 0.05) and significantly less intraoperative blood loss (median, above 27.5 vs below 50 mL, p < 0.05). Other perioperative outcomes, including surgical margin status, perioperative complication rate, as well as postoperative renal function preservation, remained similarly favorable (Table 3).

Table 3.

Comparison of Perioperative Outcomes Between Single-Port Robotic Partial Nephrectomy Cases with Likelihood Ratio Above or Below the Calculated Optimal Cutoff of 0.12

	Likelihood ratio below 0.12	Likelihood ratio above 0.12	p
n (%)	135 (72%)	54 (28%)
Total operating time (minutes), median (IQR)	139.5 (98.8–190.3)	162.5 (127.8–181.5)	0.127
Ischemia time (minutes), median (IQR)	19 (15–25)	11 (9–16)	<0.05
Estimated blood loss (mL), median (IQR)	50 (30–100)	27.5 (25–50)	<0.05
Intraoperative complication, n (%)	2 (1.6%)	0 (0%)	0.959
Positive surgical margin, n (%)	7 (6.4%)	1 (2%)	0.442
Length of hospital stay (days), median (IQR)	1 (1–1)	1 (1–1)	0.596
90-day postoperative complication, n (%)	11 (8.6%)	1 (2.2%)	0.269
Major postoperative complication, n (%)	4 (4.5%)	0 (0%)	0.365
Postoperative GFR (mL/min/1.73m²), median (IQR)	69.3 (62–82.9)	87 (61–100.1)	<0.05
Postoperative %GFR preservation, median (IQR)	93.3 (86–101.8)	98.4 (88.4–104.2)	0.118
Postoperative CKD stage			0.059
CKD Stage 1, n (%)	4 (11.8%)	20 (43.5%)
CKD Stage 2, n (%)	23 (67.6%)	15 (32.6%)
CKD Stage 3a, n (%)	2 (5.9%)	7 (15.2%)
CKD Stage 3b, n (%)	3 (8.8%)	4 (8.7%)
CKD Stage 4, n (%)	0 (0%)	0 (0%)
CKD Stage 5, n (%)	2 (5.9%)	0 (0%)
Clinically significant CKD upstaging compared to baseline, n (%)	2 (5.9%)	6 (13%)	0.498

Major postoperative complication defined as those of Clavien–Dindo grades 3a and above. CKD stage was defined according to the NKF KDOQI with CKD 1 ≥ 90 mL/min/1.72 m²; CKD 2 = 60–89 mL/min/1.72 m²; CKD 3a = 45–59 mL/min/1.72 m²; CKD 3b = 30–44 mL/min/1.72 m²; CKD 4 = 15–29 mL/min/1.72 m²; and CKD 5 ≤ 15 mL/min/1.72 m². Clinically significant CKD was defined as any progression from CKD Stages 1–2 to 3a or above, from 3a to 3b or above, from 3b to 4 or above, or from 4 to 5.

GFR = glomerular filtration rate.

Discussion

The introduction of the purpose-built SP platform has allowed for an expanded armamentarium of minimally invasive nephron-sparing surgical approaches and paved the way for the implementation of more regionalized and less invasive surgical techniques. Although earlier studies have shown comparable oncological and functional outcomes between SP and MP-RPN,^15

–19 the more regionalized SP approaches, such as the innovative LAA retroperitoneal technique, have been demonstrated to confer enhanced postoperative recovery favoring opioid-free same-day discharges and improved patient comfort.⁹ However, despite these advances and with the increasing adoption of the SP, there remains a paucity of evidence and consensus regarding the appropriate patient selection criteria for the two surgical modalities.

To our knowledge, this study represents the first to develop an evidence-based patient-selection algorithm when considering between SP vs MP-RPN, drawing from a large multi-institutional database comprising 1021 patients. Our nomogram incorporates variables identified as statistically significant predictors of SP-RPN through multivariate analysis. It is noteworthy that our algorithm favors patients with fewer comorbidities and tumors of lower complexity, as indicated by the lower ASA and the different RENAL score components, respectively. This preference may stem from the initial patient selection and cases performed during the early learning curve of SP-RPN, which may also be confounded by the varying degrees of experience with the SP platform across the different institutions. Nevertheless, this consecutive series of patients were included to reduce the risk of selection bias and to offer a more practical guide for centers wishing to incorporate the SP into an already established MP program.

In assessing the clinical utility of this novel nomogram, we have found that strong adherence to our model, as exemplified by the SP-RPN cases scoring above the calculated optimal likelihood ratio of 0.12, was correlated with significantly improved perioperative outcomes. These findings align with existing literature comparing the perioperative outcomes between SP and MP-RPN.^15

–19 Of note, while previous propensity-matched analyses based on various baseline clinicodemographic variables identified comparable perioperative outcomes between the two surgical approaches, further subanalysis based on the tumor complexity revealed increased operating time and ischemia time during SP-RPN for high-complexity tumors compared to the MP approach.^15,16 Although these differences could be attributed to the learning curve of the individual surgeons, variations in operating and ischemia times may also be secondary to the technical differences between the two platforms, such as the reduced grip and dissection strength of the SP instruments, which were designed to improve ergonomics, maneuverability, and precision in limited surgical working space.^4,20

Among the various components of the RENAL scores, the anterior or posterior location of the tumor was not identified as an independent predictor of SP vs MP-RPN. However, it is crucial to acknowledge the technical nuances involved when operating on tumors located in the different positions using the two robotic platforms. In MP-RPN, accessing anterior tumors typically relies on the transperitoneal approach, while posterior tumors can also be accessed via a retroperitoneal approach.²¹ This necessity to adapt surgical approaches and port placements based on tumor locations was not as apparent with the more regionalized SP LAA retroperitoneal approach. With SP LAA, a single incision placed consistently at two fingers’ breadth above the superior pubic ramus can be generalized for use in anterior, posterior, or laterally located tumors without the need for additional ports.

While previous studies have underscored the comparable perioperative outcomes between transperitoneal and retroperitoneal approaches,^7,8 it is crucial to recognize the incremental value provided by the SP and its innovative techniques, particularly in improving postoperative recovery.⁹ Notably, the technique’s association with reduced postoperative pain and shorter hospital stays may be attributed to the limited dissections through the musculature and the preservation of accessory respiratory muscles. Furthermore, direct access and confined dissection within the retroperitoneal space minimize the risk of peritoneal irritation, such as from peritoneal insufflation and bowel manipulation, as commonly required in the MP transperitoneal approach.⁹ In addition to these benefits, the complete preservation of the peritoneum with regionalized SP LAA approach also proves to be a valuable alternative when considering RPN in patients with a hostile abdomen, with early experiences demonstrating its safety and feasibility.

This study is not without limitations with the first relating to its retrospective nature that is prone to selection bias. Of note, it remains difficult to capture the different learning curves of the individual surgeons and ascertain why certain patients were referred for one approach compared with the other. Second, the multi-institutional nature of the database posed additional challenges, such as in terms of missing data and heterogeneity in reporting. To mitigate the influence of these factors, we have only included variables that have been consistently reported by the participating institutions. Given the evolving nature of the field, we also identified some heterogeneity in the current SP practices, including the use of the transperitoneal approach, as well as retroperitoneal access performed via flank incision and LAA, as described in our database. Of note, the introduction of the SP techniques has also facilitated an increased adoption of the retroperitoneal approach, especially with it representing 62.5% compared with 25% of MP-RPN. Nevertheless, this nomogram was constructed to provide more comprehensive guidance for all renal masses, hence improving its versatility. It also remains important to recognize that while the SP platform can be effectively utilized to replicate the standard MP-RPN approaches, the SP techniques should not be considered a replacement for the MP. Rather, the utility of the novel SP techniques, such as the LAA, should be considered for their additional value to our patients and enrich the repertoire of our contemporary minimally invasive surgical approaches for nephron-sparing surgery.

Conclusions

Herein, we have constructed a novel patient-specific nomogram to assist in the preoperative clinical decision-making when choosing between SP vs MP-RPN. The comprehensive analysis of various baseline clinicodemographic variables that underscore our nomogram, especially relating to the patient’s comorbidity and tumor characteristics, offers valuable insights for institutions seeking to incorporate the SP platform into their practice. Although further research remains required to provide external validation, this nomogram can be leveraged as an additional tool to ensure the favorable perioperative outcomes associated with the expanding repertoire RPN procedures.

Footnotes

Authors’ Contributions

Conceptualization and Design: N.A.S. and J.K. Data acquisition: N.A.S., K.E.O., R.R.-C., R.S.C., Y.W., C.M., E.S., M.R., I.S., J.S.C., C.D.M., A.M.P., M.A., M.D.S., C.R., A.L., R.A., B.Y., R.J.N., S.C., K.K.B., and J.K. Supervision: M.A., M.D.S., C.R., A.L., R.A., B.Y., R.J.N., S.C., K.K.B., and J.K. Statistical analysis and data interpretation: N.A.S. Drafting of article: N.A.S. Critical revision of article: M.A.., M.D.S., C.R., A.L., R.A., B.Y., R.J.N., S.C., K.K.B., and J.K.

Author Disclosure Statement

J.K. is a speaker for Intuitive Surgical Inc. and is a consultant for MethodAI, VTI, and EndoQuest Robotics. M.A. is a consultant for Intuitive Surgical Inc., Aminox/Clarix, and VTI. M.D.S. serves on the scientific advisory board for Intuitive Surgical Inc. and is a consultant for VTI and Ethicon. S.C. is a consultant for Intuitive Surgical Inc. The remaining authors have no conflicts of interest to disclose.

Funding Information

No funding was received for this article.

Supplementary Material

Supplementary Figure S1

Supplementary Table S1

Abbreviations Used

References

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Supplementary Material

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