Standardization of Surgical Outcome Across the Tumor Complexity Spectrum in Robotic Partial Nephrectomy

Abstract

Introduction:

Standardization of surgical steps or techniques can decrease error rates, increase efficiency, and ensure reproducible outcomes. In this study, we aimed to analyze the benefit of a standardized approach to robotic partial nephrectomy (RPN) on the reproducibility of outcomes across different tumor complexities.

Methods:

A single-center study of patients who have undergone a transperitoneal robotic-assisted partial nephrectomy for kidney cancer using the first assistant sparing technique between May 2014 and March 2022 was performed. Overall, 496 patients were included in the analysis. We compared clinical data and perioperative and postoperative outcomes for low, moderate, and high complexity score renal tumors. Tumor complexity was stratified using the Radius, Exophytic/Endophytic, Nearness to the collecting system or sinus, Anterior/Posterior, Location relative to the polar line nephrometry score. Data were compared using Kruskal–Wallis test, Chi-square test of Independence, and Fisher's exact test.

Results:

Of the patients in the study, 54.64% were low tumor complexities (n = 271), 40.32% were moderate tumor complexities (n = 200), and 5.04% were high tumor complexities (n = 25). High tumor complexity patients had significantly longer operative time (149 minutes versus 137 minutes moderate complexity versus 125 minutes low complexity, P = .001), longer ischemia time (12 minutes versus 11 minutes intermediate versus 10 minutes low complexity, P = .0001), and significant reduction in estimated glomerular filtration rate (−12.58 mL/min/1.73 m² versus −5.51 mL/min/1.73 m² intermediate versus −3.08 mL/min/1.73 m² low complexity, P = .005). There was no significant difference in estimated blood loss (P = .074), blood transfusion rate (P = .454), postoperative complication rate (P = .527), surgical complication rate (P = .210), major complication rate (P = .098), length of hospital stay (P = .583), positive surgical margins (P = .872), and trifecta achievement (P = .740).

Conclusion:

Irrespective of tumor complexity, approaching RPN using a standardized approach will offer patients favorable perioperative outcomes. This approach has standardized our preoperative counseling, patient expectation, and postoperative surgical pathway across the tumor complexity spectrum.

Introduction

Extirpative surgery through partial nephrectomy (PN) is the gold standard treatment to treat localized renal tumors amenable to nephron-sparing surgery (NSS). Guidelines also recommend NSS, regardless of approach, for cT1a and cT1b staged renal masses when feasible.¹ Traditionally, open surgery was considered the gold standard approach to performing NSS. With the rise of minimally invasive treatment options over the past decades, robotic partial nephrectomy (RPN) has now become the most common surgical modality used to treat localized renal tumors.²

Currently, RPN outcomes are variable and largely based on surgeon experience and tumor characteristics—a byproduct of the lack of standardization of the procedure. And while the guidelines describe PN as the optimal treatment modality,³ the lack of specification regarding surgical approach limits surgeon adherence to proposed guidelines. As such, high-volume centers are found to adhere to guidelines better than low-volume centers.⁴ Standardizing and optimizing the approach to RPN will ultimately have multifaceted benefits. There will be an increase in surgeon use of the optimal technique, an increase in the production of reproducible data, and an overall improvement in measurable patient outcomes regardless of tumor complexity. Hence, the purpose of this study is to evaluate the benefit of utilizing a standardized approach in optimizing outcomes across renal tumor complexities.

Patients and Methods

Surgical approach and technique

The previously published first assistant sparing technique (FAST) was utilized for all cases.⁴ The approach has been optimized in such a way that every patient undergoes the surgery with the same setup irrespective of tumor size or location, including positioning, port placement, steps of procedure, instrumentation, and steps of renorrhaphy. Briefly, patients are positioned in flank position with the surgical bed flexed at maximum. Axillary roll is placed to avoid shoulder injury and appropriate padding is applied to pressure points. The Da Vinci^® Xi System was used for all procedures. After establishment of the pneumoperitoneum, four 8 mm robotic trocars are placed in a linear manner along the midclavicular line. Robotic ports are at equal distance from each other. A 12 mm assistant port is placed between the two proximal trocars. For right sided kidney surgeries, an additional 5 mm assistant trocar is placed for liver retraction.

After the robot is docked, monopolar scissors are used as the right-hand instrument, forced bipolar forceps is used as the left-hand instrument, and a Tip-up fenestrated grasper is used as the fourth arm instrument. For right kidneys, a self-retaining grasper is inserted through the 5 mm port, which is used to move the liver away from the right kidney. In a standard trans-peritoneal manner, the colon is mobilized medially, and ureter and gonadal vein are identified and dissected proximally. Afterward, the hilum is dissected, and the kidney mass is visualized. Using the TilePro^® feature, the ultrasound (US) probe is introduced intracorporeally. The forced bipolar forceps have a strong grasp feature that enables performing US without instrument exchange, while still maintaining the bipolar cautery function. This eliminates the use of an extra instrument, and total robotic instruments for the procedure remain at 4.

The single instrument exchange is the monopolar scissor for a needle driver during the entire procedure. After the US imaging is completed, all renorrhaphy sutures are placed intracorporeally at once. This obviates the need for multiple passes of suture material by the bedside assistant. Finally, 4 cm robotic Scalnan^® bulldog clamps are placed intracorporeally. FAST allows the console surgeon to position the kidney using the fourth arm and directly control the bulldog clamps with the forced bipolar forceps, which can be very helpful in managing difficult angles to clamp the renal artery. The renal vein is not routinely clamped. Renal vein clamping is preferred in large and hilar tumors where backflow bleeding can limit visualization.

For the initial renorrhaphy layer, a 15 cm 3-0 monofilament barbed suture on a 17 mm 1/2 curve needle (V-Loc™; Covidien, Mansfield, MA) is placed. For the second layer, three to four 15 cm 0 polyglycolic acid sutures on a 37 mm 1/2 curve needles (Vicryl; Ethicon, Somerville, NJ) are placed. For the polyglycolic acid sutures, Weck Hem-o-lok^® ligation clips (Teleflex, Research Triangle Park, NC) and absorbable suture clips (Lapra-Ty; Ethicon-Endo, Cincinnati, OH) are loaded ∼1 cm from the tail of the sutures. These sutures are stabilized to the anterior abdominal wall. After the tumor is excised, the 3.0 barbed wire suture is used to suture the collecting system and the vessels. After running the suture, Weck clips are used to stabilize sutures.

New sutures can be introduced by the assistant as required. Renal artery is unclamped early to reduce ischemia time and visualize the tumor bed for arterial bleeders to prevent pseudoaneurysm after first layer is completed. After early unclamping, the second cortex layer is closed. Weck clips are used to stabilize these sutures as well. Once the renorrhaphy is completed, all needles and clamps are removed outside the body. Surgical drain is not routinely placed.

Patients and data source

Data were obtained from our Institutional Review Board-approved single-center kidney cancer database of patients who have undergone transperitoneal robotic-assisted PN for analysis (n = 823). We identified patients who underwent transperitoneal RPN using FAST (n = 638), and all cases were performed between May 2015 and March 2022. Patients with prior ipsilateral kidney surgery (n = 10), end-stage renal disease (n = 9), multiple tumors/bilateral tumors (n = 37), horseshoe kidney (n = 5), solitary kidney (n = 11), missing Radius, Exophytic/Endophytic, Nearness to the collecting system or sinus, Anterior/Posterior, Location relative to the polar line (R.E.N.A.L) nephrometry score (n = 54), and trifecta achievement (n = 16) (7) were excluded from the analysis. Overall, 496 patients were included in the analysis.

Outcome variable

The main outcomes of interest were the perioperative and postoperative: operative time, ischemia time, estimated blood loss (EBL), length of stay (LOS), postoperative complication rates (any, surgical, and major), positive surgical margins, change in estimated glomerular filtration rate (ΔeGFR), and trifecta achievement. Major complications were defined based on the Clavien–Dindo classification.⁵ Complications were classified as major when the Clavien score was ≥3. Trifecta achievement was defined as achieving an ischemia time <25 minutes, no major complication, and negative surgical margin.

Variables

Baseline demographic, clinical, and tumor-specific variables evaluated in this study include age, gender, body mass index, Charlson-comorbidity index,⁶ baseline eGFR, tumor size, tumor laterality, and clinical stage. Tumor complexity was defined using the R.E.N.A.L nephrometry score. Patients were categorized into three groups based on tumor complexity: low tumor complexity (4–6), moderate tumor complexity (7–9), and high tumor complexity (10–12).

Statistical analysis

Descriptive statistics were performed to show the distribution of the overall population of patients included in the study. Continuous variables were presented as medians, interquartile ranges (IQRs), and ranges. Categorical variables were presented as frequencies and percentages. Since the goal of the study was to evaluate the role of a standardized surgical approach across tumor complexities, we compared baseline demographic, clinical, and tumor-specific characteristics, as well as all perioperative and postoperative outcomes by tumor complexity using Kruskal–Wallis test, Chi-square test of Independence, and Fisher's exact test. All analyses were conducted using STATA version 14.1 (College Station, TX), and statistical significance was determined at P value <.05.

Results

Baseline characteristics

Of the 496 patients included in the analysis, the distribution of tumor complexities was low (n = 271, 54.64%), moderate (n = 200, 40.32%), and high (n = 25, 5.04%). Baseline GFR (P = .037) and tumor size (P = .0001) were higher in more complex tumors. Baseline characteristics are summarized in Table 1.

Table 1.

Baseline Characteristics of Patients Who Underwent Robotic Partial Nephrectomy Using a Standardized Approach

	Tumor complexity				P
	Total	Low (4–6)	Moderate (7–9)	High (10–12)	P
	496	271 (54.64)	200 (40.32)	25 (5.04)
Age (years)^a	62 (54, 70)	63 (55, 70)	60 (52, 69)	61 (55, 65)	.159
Gender^b					.150
Female	181 (36.49)	102 (37.64)	66 (33.00)	13 (52.00)
Male	315 (63.51)	169 (62.36)	134 (67.00)	12 (48.00)
BMI, kg/m²	27.77 (24.47, 31.89)	27.55 (24.43, 31.67)	28.14 (25.18, 32.30)	27.06 (23.39, 31.50)	.693
CCI^a	3 (2, 4)	3 (2, 4)	3 (2, 4)	3 (2, 4)	.471
Baseline eGFR (mL/min/i.73 m²)^a	78.44 (66.06, 94.46)	77.55 (66.06, 91.26)	78.60 (66.24, 95.16)	99.46 (68.99, 111.57)	.037
Tumor size (cm)^a	2.80 (2.00, 3.90)	2.40 (1.80, 3.40)	3.20 (2.40, 4.80)	4.20 (3.40, 5.10)	.0001
Laterality^b					.515
Right	253 (51.01)	132 (48.71)	108 (54.00)	13 (52.00)
Left	243 (48.99)	139 (51.29)	92 (46.00)	12 (48.00)
Clinical stage^b					<.001
T1a	378 (76.21)	239 (88.19)	131 (65.50)	8 (32.00)
>T1a	102 (20.56)	25 (9.23)	62 (31.00)	15 (60.00)
Missing	16 (3.23)	7 (2.58)	7 (3.50)	2 (8.00)

Continuous variables are reported as median (IQR).

Categorical variables were presented as n (%).

BMI, body mass index; CCI, Charlson's comorbidity index; eGFR, estimated glomerular filtration rate; IQR, interquartile range.

Perioperative and postoperative outcomes

In patients managed with a standardized robotic technique, the median ischemia time was 10 minutes (IQR: 8, 14 minutes) and the median operative time was 130 minutes (IQR: 117, 152 minutes). The median postoperative EBL was 50 mL. The postoperative complication rate was 11.09% and the major complication rate was 1.01%. Median LOS was 1 day. Positive margin rate was 5.04%, and the median change in eGFR was −3.97 mL/min/1.72 m² at a median follow-up period of 6 months. Trifecta was achieved in 93.55% of patients (Table 2).

Table 2.

Operative and Postoperative Characteristics By Tumor Complexity Among Those That Had First Assistant Sparing Technique

	Tumor complexity				P
	Total	Low (4–6)	Moderate (7–9)	High (10–12)	P
Operative time (minutes)^a	130 (117, 152)	125 (114, 146)	137 (120, 156)	149 (135, 154)	.001
Ischemia time (minutes)^a	10 (8, 14)	10 (7, 12)	11 (9, 15)	12 (11, 17)	.0001
EBL (mL)^a	50 (50, 50; 20–500)	50 (50, 50; 25–300)	50 (50, 75; 20–500)	50 (50, 75; 25–200)	.074
Blood transfusion	1 (0.20)	0 (0.00)	1 (0.50)	0 (0.00)	.454
Postoperative complication^b	55 (11.09)	27 (9.96)	26 (13.00)	2 (8.00)	.527
Surgical complication^b	21 (4.23)	8 (2.95)	12 (6.00)	1 (4.00)	.210
Major complication^b	5 (1.01)	1 (0.37)	3 (1.50)	1 (4.00)	.098
LOS (days)^a	1 (1, 1;)	1 (1, 1)	1 (1, 1)	1 (1, 1)	.583
Positive margin^b	25 (5.04)	14 (5.17)	10 (5.00)	1 (4.00)	.872
ΔeGFR (mL/min/1.72 m²)^a,c	−3.97 (−12.31, 3.47; −66.79, 59.85)	−3.08 (−9.97, 4.93; −66.79, 36.27)	−5.51 (−14.34, 2.63; −65.71, 22.40)	−12.58 (−22.49, −1.71; −51.79, 1.09)	.005
Trifecta achievement	464 (93.55)	255 (94.10)	186 (93.00)	23 (92.00)	.740

Values in bold are significant at P < 0.05.

Continuous variables are reported as median (IQR; range).

Categorical variables were presented as n (%).

Change in eGFR between last follow-up and baseline.

EBL, estimated blood loss; eGFR, estimated glomerular filtration rate; IQR, interquartile range; LOS, length of stay.

In bivariable analysis, high tumor complexity had significantly longer operative time (129 minutes versus 137 minutes moderate complexity versus 149 minutes low complexity, P = .001), and longer ischemia time (10 minutes versus 11 minutes moderate versus 12 minutes low complexity, P = .0001). Similarly, high tumor complexity had significant reduction in eGFR (ΔeGFR) (−12.58 mL/min/1.73 m² versus −5.51 mL/min/18.73 m² moderate versus −3.08 mL/min/1.73 m² low complexity, P = .002).

There was no significant difference observed in EBL (P = .074), blood transfusion rate (P = .454), postoperative complication rate (P = .527), surgical complication rate (P = .210), major complication rate (P = .098), length of hospital stay (P = .583), positive surgical margins (P = .872), and trifecta achievement (P = .740) (Table 2).

Discussion

NSS is considered the gold standard treatment option for the management of T1 renal tumors. Evidence increasingly supports improved postoperative recovery and patient outcomes associated with minimally invasive NSS options. As such, RPN should be offered to patients as the primary option whenever possible.¹ Currently, despite guideline recommendations, RPN rates for surgical management of T1 renal masses do not reflect the total number of surgeries performed for T1 renal tumors—leaving room for widespread improvements in measurable patient outcomes. May et al analyzed the American College of Surgeons' National Cancer Database (NCDB) cases from 2004 to 2015 and showed that only 71.3% of cT1a renal masses undergo PN in the United States.⁷ Future updates of the NCDB will give more insight into current statistics and PN trends.

However considering how stable the rate of partial nephrectomies has been since 2012, it is reasonable to assume that new data will not reveal an increase in frequency of PNs. By providing a standardized protocol and approach to the treatment of cT1a renal masses like the FAST, we can see more surgeon adherence to RPN, leading to improvements in patient outcomes and increased collection of reproducible data, which should allow for even further optimization of outcomes.

There are multiple factors that may influence why surgeons utilize PN and RPN less frequently, despite guideline recommendations. A lack of exposure to techniques, considerable dearth of reproducible data, and perioperative complication concerns can greatly impact a surgeon's comfort with the procedure.⁸ Data show, however, that partial nephrectomies can achieve satisfactory trifecta rates in patients with complex renal masses.⁹ The outcomes reported in the literature are from high-volume centers and should be reproducible by lower volume surgeons.

To increase reproducibility, standardized approach like FAST helps combat the variability that generally plagues PN procedures. The current robotic technique addresses variability by providing an approach that utilizes the same patient position and port configuration irrespective of tumor side, size, and location. A standardized approach makes the surgical steps easier to replicate. Using this approach, we have been able to achieve similar perioperative outcomes across the tumor complexity spectrum. A standardized robotic approach consistently minimizes ischemia time regardless of tumor complexity. Low, moderate, and high complexity tumors had a median ischemia time of 10, 11, and 12 minutes, respectively. It is especially worth noting that the median ischemia time observed in this study is 10 minutes. While the median operative time (149 minutes) was higher in the high complexity group, the magnitude of variation from the other tumor complexities may not be clinically significant.

Despite these findings and the unfavorable anatomical characteristics of complex tumors, this study did not show any difference in EBL, blood transfusion rate, postoperative complication rate, major complication rate, LOS, and positive margin rates. Hence, although complex renal tumors result in a higher Warm Ischemia Time and complication rate as have been previous shown,¹⁰ RPN can be performed successfully in this cohort as well,⁹ and optimally with a standardized approach.

In the high complexity group, ΔeGFR was observed to be significantly higher (−12.58 mL/min/1.73 m² versus −5.51 mL/min/18.73 m² intermediate versus −3.08 mL/min/1.73 m² low complexity, P = .005). This is most likely due to increased parenchymal volume loss in the high complexity group rather than it being a result of the RPN technique. Ultimately, this study and data aim to allow surgeons to comfortably perform RPN with minimal concern for ischemic injury regardless of tumor complexity.

When comparing laparoscopic PN and RPN, RPN has proven to be more successful at achieving trifecta. RPN shows better perioperative outcomes, lower morbidities, and a wider range of indications along with higher trifecta rates.¹¹ With the consistent benefits that RPN displays, adopting a standardized approach to the demonstrably optimal technique will allow surgeons to provide a higher standard of care, while increasing procedure comfort and adherence. In this study, the FAST approach exhibited all the benefits of RPN, while achieving similar trifecta rates across the tumor complexity spectrum. This is especially important in management of high complexity renal masses since some surgeons feel more comfortable performing open PN in this setting to achieve optimal results.¹²

Limitations

Robotic PN has evolved in the past decade and the surgeon experience plays a key role in the favorable outcomes seen in the study. The effect of the surgeon's experience and volume has been published in the past,^13,14 and it does limit the reproducibility of our results in all practice settings. Therefore, our results should be validated in the low-volume surgeon setting. The surgeon used the same approach in every case, which limits the selection bias. It should be noted, the report does not include retroperitoneal approaches. Therefore, our results are only applicable to the transperitoneal approach. Overall, the benefit of current robotic technique is that it is a standardized approach that can be performed in every RPN case irrespective of tumor complexity, while providing similar favorable outcomes between low, intermediate, and high complexity tumors.

Conclusion

As robotic technique and instrumentation continue to evolve, the option of safe PN in more challenging tumor scenarios will continue to increase. Hence, the standardization of surgical techniques is imperative. Approaching RPN using a standardized approach—irrespective of renal tumor complexity—will offer patients favorable perioperative outcomes, increase efficiency, and ensure reproducible results.

Footnotes

Authors' Contributions

K.E.O.: conceptualization, methodology, formal analysis, writing-original draft, and project administration. A.T.B.: conceptualization, methodology, and writing-original draft. R.D.P.: writing-reviewing and editing. S.R.: writing-reviewing and editing. K.K.B.: conceptualization, methodology, and supervision.

Disclosure Statement

Authors have no conflict of interests.

Funding Information

No funding was received for this article.

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