Cost Analysis of Robot-Assisted Laparoscopic Versus Hand-Assisted Laparoscopic Partial Nephrectomy

Abstract

Purpose:

To perform a cost comparison of three approaches to partial nephrectomy (PN): Open (OPN), hand-assisted laparoscopic (HALPN), and robot-assisted (RAPN).

Patients and Methods:

We retrospectively evaluated cost and clinical data from patients undergoing OPN, HALPN, and RAPN from 2007 to 2010 (n=89). Baseline demographic data, patient comorbidities, R.E.N.A.L. nephrometry score, and perioperative outcomes were assessed. Costs and subcosts from the operating room (OR) and hospital were evaluated using nonparametric statistical analyses.

Results:

Patient demographics and tumor characteristics were similar between HALPN and RAPN, while OPN patients had more comorbidities and more difficult-to-resect tumors. Thus, HALPN and RAPN were directly compared, while OPNs were excluded from the analysis. No difference was found in overall costs between HALPN and RAPN ($13,560 vs $13,439, P=0.29). OR costs were higher for RAPN ($7276 vs $5708, P=0.0001) because of the higher robotic capital and reusable equipment costs that outweighed higher disposable costs in the HALPN group. OR time-related costs were similar between groups. RAPN patients had a shorter length of stay (LOS), which decreased postoperative hospital costs ($4371 vs $5984, P=0.002).

Conclusions:

No difference in overall cost was found between RAPN and HALPN. Robot allocation, OR equipment use, and LOS are important determinants of total cost. Further study regarding recovery and quality of life may reveal added benefits to minimally invasive approaches and increase use of nephron-sparing surgery.

Introduction

T he incidence of small renal masses (SRMs) has increased dramatically over the past 2 decades because of incidental discovery after cross-sectional abdominal imaging.¹ At the same time, the “gold standard” for the surgical management of SRMs has shifted from radical nephrectomy (RN) to partial nephrectomy (PN) and other nephron-sparing techniques because of concerns regarding the long-term risk of chronic renal insufficiency and cardiovascular mortality.^2

–6 The adoption of nephron-sparing surgery (NSS), however, has been slow and has been identified as a quality-of-care concern.^7,8 Causes for this lack of adoption are complex and are likely driven by surgeon and patient preference for the short-term benefits of a minimally invasive approach such as laparoscopic radical nephrectomy (LRN) over the potential long-term benefits of NSS that for technical reasons often necessitates an open approach (ie, open partial nephrectomy [OPN]). Laparoscopic partial nephrectomy (LPN) provides the benefits of NSS in a minimally invasive approach but is perceived to be more technically challenging than LRN, limiting its adoption to highly specialized surgical centers.⁹

Robot-assisted laparoscopic partial nephrectomy (RAPN) is a recent innovation that is designed to provide a minimally invasive NSS and that is technically feasible and thus more widely adoptable. Wristed instrumentation and three-dimensional vision facilitate resection and renorrhaphy, decrease warm ischemia time, and offer an easier learning curve, all while preserving oncologic outcomes.^10
–12

Critics of robot-assisted surgery, however, often cite high capital expenses and reusable equipment costs that are associated with this approach. Some robotic cost studies have suggested that these costs can be recouped by shortened hospital stays and more rapid patient convalescence resulting in fewer missed days off work and decreased disability insurance claims.¹³ Most analyses, however, rely on cost-modeling approaches that are susceptible to assumptions. Therefore, we undertook a microcost analysis using real-world costs to evaluate differences in perioperative costs between three NSS approaches: OPN, hand-assisted LPN (HALPN), and RAPN.

Patients and Methods

Patient population

We retrospectively gathered patient-level cost and clinical data of all adult PNs performed at our institution between July 2007 and June 2010 (n=96). Multiprocedure cases (eg, simultaneous herniorraphy) were excluded (n=7), and we retained intraopertive conversions from PN to RN and from LPN or RAPN to OPN in their original groups in an intention-to-treat analysis.

Surgical treatment

All procedures were performed by experienced academic urologists with the assistance of chief residents. Each of the approaches was performed predominantly by two surgeons: OPN—MN and EW; HALPN—RP and EW; and RAPN—MR and EW. Importantly, there was almost no time overlap between HALPN and RAPN cases. All HALPNs were performed via a hand-assisted transperitoneal approach using a GelPort^® (Applied Medical, Rancho Santa Margarita, CA), disposable trocars, and reusable instruments. RAPNs were performed via a three-arm transperitoneal approach with a da Vinci^® robotic system (Intuitive Surgical Corp., Sunnyvale, CA).

Generally, one Maryland bipolar forceps, one curved monopolar scissors, and two large needle drivers were used per RAPN case. Disposable staplers (Endopath^® ETS Articulating 45-mm linear staplers, Ethicon, Cincinnati, OH), LigaSure™ Atlas 20 cm (Covidien, Mansfield, MA), and Harmonic^® ACE shears (Ethicon, Cincinnati, OH) were used primarily in the minimally invasive cases. Hilar control was obtained via bulldog clamping. Renorrhaphy was performed via the sliding clip technique in all minimally invasive approaches.¹⁴

OPNs were performed via a flank or subcostal approach. Tisseel^® (Baxter Inc., Irvine, CA), Floseal^® (Baxter Inc, Irvine, CA), and Surgicel^® (Ethicon, Cincinnati, OH) were used selectively to aid with hemostasis of the kidney defect. Operating room (OR) time was from patient entrance to exit, and case time was from incision to closure. Importantly, only OPN patients (or conversions to OPN) received continuous epidural catheter anesthetic infusion (hereafter referred to as epidural) for postoperative pain management, which was reflected in overall costs. Discharge timing was at the discretion of the surgeon, but all patients were treated using a well-defined postoperative care pathway.¹⁵

Data collection

Patient-level itemized cost data for the operation and the postoperative hospitalization were collected from the University of North Carolina (UNC) OR and hospital accounting departments. Patient and tumor information including age, sex, race, body mass index (BMI), Charlson Comorbidity Index (CCI),¹⁶ R.E.N.A.L. (radius; exophytic/endophytic; nearness; anterior/posterior; location) nephrometry score,¹⁷ and perioperative course (intensive care unit [ICU] admissions, and length of stay [LOS]) were collected from the medical record. Because Clavien grade I to II complications are unreliable in retrospective data, and because there were no Clavien grade III or V complications in our data set, we used ICU admissions (the definition of Clavien grade IV complications) as a surrogate marker for overall complications. We included real-world cost data from the entirety of the perioperative hospitalization, but some subcosts are not specifically allocated by accounting in a manner that provides cost differences for our differential cost analysis and were therefore corrected and/or modeled as discussed below.

All data were collected and handled in compliance with UNC Institutional Review Board requirements. This cost analysis is from the healthcare system perspective and is designed to capture the entirety of costs (not charges) from the surgery and perioperative hospitalization.¹⁸ Of note, because of the relatively low inflation rates (average 1.7%) and short time span of the study, unit costs were not artificially set over time.

Hospital cost collection

Patient-level itemized accounting costs obtained from the UNC hospital accounting department included overall OR costs and itemized hospitalization costs (postanesthesia recovery room costs, hospital room and board, medications (including blood transfusion), laboratory studies (including pathology), radiology, ancillary services, physical therapy/occupational therapy, etc). Generally, total OR costs in these data represent the sum of OR capital expenses/overhead, time fees, and disposable/reusable equipment, and only sutures, staples, clips, and implants are allocated at the patient level. OR allocation patterns are institution-specific, and at our institution, there are four base fee levels, each of which (in theory) represents increasing resource utilization. OPN cases generally receive an OR base fee of three (cost: $1252), and minimally invasive procedures such as HALPN/RAPN receive an OR base fee of four (cost: $2200), which (theoretically) accounts for the increased expenditures in minimally invasive cases. Because these base-fee allocations did not provide the differential cost resolution needed for our analysis, we set the base fee for each procedure to be $1252 and sought to determine the differential cost from OR resource allocation more accurately (described below).

OR overhead cost calculation for HALPN and RAPN

Our strategies to calculate differential cost attributable to differences in capital expenses and reusable equipment allocation depended on the availability of the cost and allocation data of the different surgical approaches. Calculating the additional overhead cost attributable to performing a case laparoscopically (nonrobotic) (HALPN) proved to be an extraordinarily difficult task. The data we needed (cost of equipment [video equipment, laparoscopes, etc], equipment maintenance contracts, and more importantly, the allocation basis of such equipment) were difficult to obtain because of dispersion across multiple departments and cost centers and origination from multiple vendors. In addition, used reusable laparoscopic surgical tools are sold to a service vendor that services the equipment before selling them back to the hospital at a discounted price. Thus, both cost and item-use allocation are difficult to define. Not surprisingly, these overhead cost data for laparoscopic surgeries are nearly always ignored in the literature but were estimated for laparoscopic colonic resection in 2004.¹⁹ These data were converted from 2001 Euros to 2010 United States dollars to provide a point-estimate of these costs in our analysis ($200).

These overhead costs for the robot-assisted approach are much more easily definable, because all of the equipment (robot, reusable equipment, insufflators, video towers, etc) is from the same vendor, maintained under the same maintenance contract, and its usage pattern is accurately recorded. For example, the endoscopes are used only on robotic cases, and the reusable equipment (scissors, needle graspers, etc) can only be used a preset number of times (10) before disposal (“reposable”). Finally, this equipment is only used on robotic cases, and the number of robotic cases is known and offers an exact denominator.

Other groups have taken a line-item approach to robotic expenses, but we thought that this might neglect “real-world” usage (equipment upgrades, broken endoscopes, etc). Thus, we calculated the average of yearly expenditures to the robotic vendor (Intuitive, Inc), amortized any large (>$100,000) capital expenses over 7 years, and averaged the yearly expenses from fiscal year 2005 to 2010. Large capital expenses included two four-arm da Vinci S systems with HD upgrades (one each in 2005 and 2007). We then divided this cost by the number of robotic cases performed (ranging from actual 70% usage to ideal 100% usage) to obtain a range of point estimates for robotic overhead per case. For our analysis, we elected to use $2000 or about 80% usage as a point estimate for robotic capital expense and performed one-way sensitivity analysis on this point estimate. Notably, our line-item analysis for RAPN also approximated this value (see Addendum, Supplementary Table 1).

Finally, the overhead for OPN was approximated to be $50,¹⁹ which theoretically should be included in the OR base fee three. Thus, $50 was subtracted from HALPN and RAPN overhead point estimates to avoid double counting.

Disposable equipment costs for HALPN and RAPN

For disposable expenses, we obtained the case-specific logs of bar code-scanned disposable items from the UNC OR accounting office. Bar codes of each item are scanned by a circulating nurse during the surgery and added to a per-case expense total. Nonimplant disposables include: GelPort,^® staplers, Ligasure.™ and Tisseel^® applicators, Harmonic^® shears, trocars, Endopouch^® retrieval bags, drapes, and gloves. We confirmed the use of expensive items (GelPort, staplers, Ligasure, Harmonic shears) in the operative reports to ensure bar code scanner data reliability. Costs of implantable disposables from the hospital data were added to costs of nonimplantable disposables from the OR data to obtain the total disposable costs. It was assumed that an OR base fee of three matched the allocation basis of OR overhead and disposable use for the OPN procedure. Thus, the averages for these costs in the OPN group were subtracted from overhead and disposable costs for HALPN and RAPN cases to yield the costs represented by resource utilization in addition to that of an OR base fee of three procedure (ie, to avoid double counting).

Other costs

Professional fees of surgeons, anesthesiologists, radiologists, and consulting physicians were collected from the accounting department and included in the analysis.

Finally, we inductively identified any differences in clinical care between the groups and sought to calculate the differential costs attributable to that care. Because of the pain associated with a muscle-cutting subcostal incision, most patients undergoing OPN receive an epidural for pain management. Professional fees were $625 for placement and $360/day for maintenance, for an average of 2 days, for a total of $1445. We multiplied this by a standard cost/charge ratio of 0.5 to obtain a cost of $725, added the $200 materials fee for a total cost of $925, and then multiplied by the fraction of cases receiving an epidural to get the attributable cost per case in each group.

Overall cost calculation and subcost analysis

To calculate overall cost, we added the total hospital cost, the OR disposable costs, the calculated robotic and laparoscopic capital/maintenance expenses and reusable equipment costs, and physician professional fees. For the subcost analysis, we used the total hospital cost data and separated OR-specific fees from postoperative costs. Further, we evaluated differential costs among groups either by department (pathology, laboratory, pharmacy), by line item (transfusion, analgesia), or by hospital day (we specifically calculated discharge day −1, because this represents the total cost of room and board plus laboratory charges plus medications that could be saved by discharging the patient 1 day earlier).

Statistical analysis

All statistical analyses were performed with SAS^® v9.2 (SAS Institute Inc., Cary, NC). Unless otherwise noted, the overall cost data herein are distributed in a right-skewed pattern (similar to most healthcare cost data),^20,21 and according to convention in cost studies, point estimates are presented as means, and nonparametric statistical analyses are used (Mann-Whitney U for two-way, and Kruskal-Wallis for three-way analyses).²² Severe cost outliers (one from HALPN group, one from RAPN group, each ∼$45,000; 4×median cost for group) were confirmed using extreme studentized deviate outlier test Z=5.25, and excluded to allow for analysis of “routine” cases. To evaluate the impact of patient and tumor variables on overall cost, a multivariate regression analysis using all three groups was performed (results presented in the addendum). Finally, sensitivity analysis was performed on modeled point estimates (such as the capital costs of HALPN/RAPN) to evaluate their impact on total costs using TreeAge Pro v2011. All reported P values are two-sided, and statistical significance was set at P≤0.05.

Results

To ensure that cost differences were because of surgical approach and not patient or tumor differences between groups, we evaluated groups on various clinical and tumor characteristics. Patient age, sex, race, BMI, CCI, and R.E.N.A.L. nephrometry score were tabulated. As expected, OPN patients were older, had more comorbidities, and more difficult-to-resect tumors (Table 1). On the other hand, HALPN and RAPN groups were remarkably similar in nearly all variables evaluated including age, race, BMI, CCI, and R.E.N.A.L. scores. Because the OPN group clearly represented a different patient and tumor population, we focused our analysis on comparison between HALPN and RAPN but included OPN data for readers' interest.

Table 1.

Patient and Tumor Baseline Characteristics

Variable	OPN	HALPN	RAPN	P values ^*
Number of cases	25	33	31
Average age (y)	57.1	51.1	51.0	0.09 (OPN vs RAPN)
				0.81 (HALPN vs RAPN)
Race (count)
White	15	28	26
Black	5	4	4
Other	5	1	1	0.99 (HALPN vs RAPN)
Sex count
Male	13	24	13
Female	12	7	18	0.02 (HALPN vs RAPN)
BMI, kg/m²	31.2	30.4	30.4	0.83 (HALPN vs RAPN)
Charlson Comorbidity score	2.60	2.06	1.97	0.04 (OPN vs RAPN)
				0.68 (HALPN vs RAPN)
R.E.N.A.L. nephrometry score	R: 1.58	R: 1.16	R: 1.16	0.007 (OPN vs RAPN)
				0.97 (HALPN vs RAPN)
	E: 1.71	E: 1.45	E: 1.36	0.03 (OPN vs RAPN)
				0.55 (HALPN vs RAPN)
	N: 2.25	N: 1.77	N: 1.81	0.09 (OPN vs RAPN)
				0.87 (HALPN vs RAPN)
	A: a-13, x-5, p-6	A: a-13, x-2, p-17	A: a-15, x-3, p-13	0.44 (HALPN vs RAPN)
	L: 2.04	L: 1.5	L: 1.7	0.36 (HALPN vs RAPN)
	Hilar: 9/25	Hilar: 3/33	Hilar: 1/31	0.002 (OPN vs RAPN)
				0.31 (HALPN vs RAPN)
	Side: 46% right	Side: 44% right	Side: 61% right	0.17 (HALPN vs RAPN)
Intraoperative conversion
To OPN	N/A	1	3
To laparoscopic radical	N/A	3	1
To open radical	1	1	0	0.31 (HALPN vs RAPN)
Fiscal year of surgery
2008	1	16	3
2009	8	12	3
2010	16	5	25	< 0.0001 (HALPN vs RAPN)
Surgeons
1	11	1	2
2	4	12	3
3	1	0	11
4	7	18	14
5	2	2	1	< 0.0001 (HALPN vs RAPN)

Continuous and categorical variables were tested using Mann-Whitney U test and the Fisher exact test, respectively.

OPN=open partial nephrectomy; HALPN=hand-assisted laparoscopic partial nephrectomy; RAPN=robot-assisted partial nephrectomy; BMI=body mass index. R.E.N.A.L. score=radius; exophytic/endophytic; nearness; anterior/posterior; location. Side, hilar.

To evaluate whether surgical variables differed between HALPN and RAPN, we tabulated surgeon, year of surgery, and intraoperative conversion and compared groups. Surgeon and year of surgery differed significantly between RAPN and HALPN, but multivariate regression analysis demonstrated that these variables (along with sex) were not independent predictors of overall cost (Addendum, Supplementary Results). In fact, while HALPN cases were mostly performed in 2008 to 2009, nearly all of RAPN were performed in 2010, suggesting that these groups represent the same patient population receiving the preferred minimally invasive approach in different years. Finally, procedures for five HALPN patients underwent intraoperative conversions, while four RAPN had their procedures converted, but these differences were not statistically significant.

Total overall costs were not different between HALPN and RAPN (means: $13,560 vs $13,439, P=0.29) (Table 2). Mean overall OR costs were significantly higher for RAPN compared with HALPN ($7276 vs $5708, P<0.0001), which were offset by higher mean post-op hospital costs for HALPN ($5984 vs $4371, P=0.0002). Epidural costs were significantly higher for OPN, which, along with higher postoperative hospital costs contributed to this group's higher mean overall cost despite lower OR costs and lower physician fees.

Table 2.

Overall Costs

Variable	OPN	HALPN	RAPN	MWU P value (HALPN vs RAPN)
Postoperative hospital cost	$6804 (5553–8054)	$5984 (4771–7198)	$4371 (3683–5058)	0.0002
OR costs	$5017 (4701–5332)	$5708 (5431–5986)	$7276 (6949–7604)	0.0001
Epidural fee/case	$925×19/25=$703	$925×1/33=$28	$925×2/31=$60	0.53
Surgeon fees	$1541	$1719	$1719	n/a
Consultant fees	$45 (0–90)	$120 (0–240)	$14 (0–28)	0.44
Total overall costs	$14,110 (12666–15554)	$13,560 (12149–14971)	$13,439 (12618–14260)	0.29

Point estimates are means with 95% confidence intervals. OR costs include OR base fee+OR time fee+anesthesia time fee+disposables+overhead point estimates+pathology+hemostatics. Surgeon fees are based on CMS reimbursements. Consultant fees represent inpatient consulting physician fees and radiologist fees.

OPN=open partial nephrectomy; HALPN=hand-assisted laparoscopic partial nephrectomy; RAPN=robot-assisted partial nephrectomy; OR=operating room; MWU=Mann–Whitney U.

Why were overall OR costs higher for RAPN? When evaluating OR subcosts, no difference was found between groups for the sum of OR base fee, OR time fees, and anesthesia time fees (RAPN vs HALPN, $3876 vs $3879, P=0.48), reflecting similarities in OR time between groups (243 vs 236 mins, P=0.39)(Table 3). The differences in OR costs between RAPN and HALPN, however, were largely attributable to calculated overhead costs that included robot capital expenses/maintenance contracts and reposable instruments (RAPN $1950/case vs HALPN $150/case). In fact, this difference overcame the more expensive use of disposable instruments in the HALPN group ($1009 vs $669, P=0.0085), which was primarily because of the GelPort cost of $480 and higher use of expensive disposable equipment such as Ligasure, Harmonic shears, and staplers (30% HALPN vs 16% RAPN, Pearson chi-square P=0.03). Statistically, significant differences were also found for hemostatic and pathology costs, but these differences were comparatively small and contributed little to the overall cost difference.

Table 3.

Operating Room Subcosts and Usage

Variable	OPN	HALPN	RAPN	P value (HALPN vs RAPN) ^a
OR base fee+time fee+anesthesia fees	$3969	$3879	$3876	0.48
OR time (min)	250 (228–272)	236 (220–253)	243 (227–260)	0.39
Unaccounted for overhead costs^b	$0	$150	$1950	n/a
Unaccounted for disposables^b	$0	$1009 (864–1155)	$669 (487–551)	0.0085
GelPort use	0%	100%	6%	<0.0001 (chi–square)
Expensive disposables usage
LigaSure/Harmonic	16%	39%	16%	0.03 (chi–square)
stapler	12%	30%	16%	0.18 (chi–square)
Hemostatics	$812 (661–963)	$526 (434–619)	$619 (532–707)	0.04
Pathology	$289 (211–367)	$321 (256–385)	$189 (147–229)	0.006

Point estimates are means (95% confidence intervals). OR time is patient entrance to exit.

P values are Mann–Whitney U unless otherwise noted.

“Unaccounted for” was calculated by subtracting the average cost of the OPN group from each patient's cost to correct to an OR base fee of three and avoid “double-counting” these costs as represented by the base fee (see Methods for more detail). Overhead costs include laparoscopic equipment, video towers for HALPN, and robot purchase/maintenance and reposable equipment for RAPN. “Disposables” includes expenses for GelPort, Ligasure, Harmonic shears, staplers, as well as drapes, gloves, etc. LigaSure/Harmonic use was mutually exclusive and thus were counted together. “Hemostatics” include costs for Tisseel, Floseal, Surgicel.

OPN=open partial nephrectomy; HALPN=hand-assisted laparoscopic partial nephrectomy; RAPN=robot-assisted partial nephrectomy; OR=operating room.

Postoperative hospitalization costs were lower for RAPN than HALPN, which were driven primarily by a decrease in the average LOS (2.45 vs 3.48 days, P=0.001) and resultant lower room and board costs ($2500 vs $3609, P<0.001) (Table 4). Postanesthesia care unit costs were slightly higher for HALPN vs RAPN ($695 vs $613, P<0.001). Postoperative ICU stays as a surrogate for complications were higher in HALPN compared with RAPN (4 vs 2), but were low in number, and this difference was not statistically significant. Other hospital subcosts (medications, laboratory) varied proportionate to LOS as expected and contributed to the overall difference between groups. The mean total cost of the last full hospital day was calculated to be $1100, which represents the potential savings by the decreased LOS for RAPN. No significant differences were found between RAPN and HALPN for transfusion or analgesic costs, and no patients in these two groups were placed on hemodialysis.

Table 4.

Postoperative Hospitalization Subcosts

Variable	OPN	HALPN	RAPN	P value (HALPN vs RAPN) ^*
PACU	$708 (635–780)	$695 (629–762)	$613 (587–639)	< 0.001
Room and board	$3845 (3219–4471)	$3609 (2814–4405)	$2500 (2057–2943)	< 0.001
LOS (d)	3.96 (3.35–4.5)	3.48 (2.99–3.99)	2.45 (2.07–2.83)	0.001
ICU count	2	4	2	0.67 (Fisher)
Transfusion	$176 (n=7)	$84 (n=5)	$79 (n=5)	0.86
	(51–301)	(3–172)	(7–150)
Analgesics POD ≥1	$95 (67–123)	$80 (56–104)	$66 (49–82)	0.43
Meds POD ≥1	$600 (473–627)	$554 (352–757)	$376 (237–515)	< 0.001
Labs POD ≥1	$139 (108–171)	$121 (91–152)	$88 (66–111)	0.017

Point estimates are means (95% confidence intervals). All costs from the laboratory (Labs) and pharmacy (Meds and Analgesics) were summed from postoperative day 1 (POD ≥1) until discharge to avoid including intraoperative expenses and to evaluate differential costs from length of stay (LOS). These costs are not all-inclusive and thus should not be expected to sum to totals in Table 2.

P values are Mann-Whitney U unless otherwise noted.

OPN=open partial nephrectomy; HALPN=hand-assisted laparoscopic partial nephrectomy; RAPN=robot-assisted partial nephrectomy; PACU=postanesthesia care unit; ICU=intensive care unit.

Discussion

These data suggest that for PNs for SRMs, the large capital costs of RAPN are offset by decreased postoperative hospitalization costs and decreased disposable equipment costs and may result in cost equivalency with HALPN. This is the first real-world cost analysis of RAPN. Recently, Mir and associates,²³ using a cost-modeling approach with abstracted data, found RAPN to be $1652 costlier than LPN, although complications, LPN overhead costs, and differences in laboratory/medication costs were not considered, potentially biasing overall costs in favor of LPN. We think that our real-world approach, which avoids cost modeling that is susceptible to modeling assumptions and bias, more accurately reflects the real-world cost implications of the robotic approach to PNs. Furthermore, our single-institution design facilitates careful evaluation of patient and tumor characteristics, less variability in operative and postoperative care, accurate cost data, and de novo identification and evaluation of previously unknown covariables.

A potential limitation to our approach is its retrospective single-institution design, which could introduce bias and affect generalizability. When comparing our costs and outcomes to other studies, however, our findings were similar. LOS was shorter in the RAPN group compared with LPN, which has been found elsewhere.^11,12,23,24 Further, the $1000/d room and board cost at our institution is at the midpoint of the range of previously reported studies ($745–$1191).²⁵ Our LPN approach was hand-assisted, which could potentially lengthen LOS because of a larger, more painful incision, shorten OR time, and increase disposable costs compared with the pure laparoscopic approach. The final effect of the hand-assisted approach on overall cost is variable, and studies have shown both higher and lower total costs compared with a pure laparoscopic approach.^26,27 Importantly, HALPN is a more technically feasible approach and likely represents the more widely used minimally invasive surgery, which increases the generalizability of these results and is important when considering these data from the healthcare policy perspective.^28,29

Finally, because of the retrospective nature of the study and the nonoverlap of RAPN and HALPN cases over time, it is possible that the difference in LOS could be attributable to changes in discharge criteria over time. We think, however, that the implementation of our postoperative pathway by the same set of surgeons was similar over the 3 years of the study and that the difference in LOS is attributable to differences in postoperative pain and perhaps differences in surgeon and patient expectations of the postoperative course. Furthermore, the year of surgery was not found to be an independent predictive variable of total overall cost in our multivariate analysis (see Addendum, Supplementary Results).

LOS could also have been affected by higher rates of ICU admissions (as a surrogate of postoperative complications) in the HALPN group (12%) compared with RAPN (6%) (although this difference was not statistically significant). To assess these effects, these patients were excluded, and the remaining sample was analyzed to identify an effect on LOS, postoperative costs, and overall costs. This reduced the difference in postoperative costs between HALPN and RAPN to $643, but this difference (along with the difference in LOS) was still statistically significant (P value of<0.001), and we still did not detect a significant difference in overall costs.

Notably, other large multi-institutional studies have shown higher rates of postoperative complications (10.2% vs 8.5%) and postoperative reexploration (6.2% vs 2.5%) in patients undergoing LPN vs RAPN, but these events are rare and differences have not reached statistical significance.^11,24 At this point, it is difficult to know whether patients undergoing RAPN truly experience fewer complications, with resultant decreases in LOS and postoperative costs, and it is likely that large prospective trials would be necessary to fully characterize these rare events and their cost implications. If higher intensive care requirements truly exist in HALPN patients, however, then our data reflect this additional cost.

The point estimates for overhead costs of laparoscopic and robotic equipment have a significant effect on the total costs. Our point estimate for robotic purchase and maintenance costs is $895/case and is within the range of other published studies.^25,30,31 Sensitivity analysis on these point estimates reveals that the total cost is far more sensitive to robot overhead cost than to HALPN overhead cost. Ideal conditions for the robot (400 cases/robot-year and 10-year allocation) yielded a point estimate of $520, while a “worst-case” scenario (100 cases/robot-year and 5-year allocation) increased the per-case estimate to $2660 (see Addendum, Supplementary Table 1). As has been shown in other studies, robotic volume is critical for cost-effectiveness, and it appears that the volume at our institution is generalizable. The reader can use the data in the Addendum, Supplementary Table 1, to calculate the per-case cost based on their robotic volume.

Finally, these costs represent costs from the perioperative hospitalization. This is likely to represent the largest cost contribution for SRMs that most likely will never need further intervention or chemotherapy. Further, there is no known difference in preoperative workup, postdischarge complications, or follow-up between HALPN and RAPN. Differences in postoperative convalescence and quicker return to work, however, are not captured in this study and could add further support for the cost-efficiency of the RAPN approach.

In sum, any novel surgical technique must demonstrate: (1) Equal or superior clinical outcome for patients, (2) ease of implementation, and (3) cost efficiency on a large scale. While RAPN appears to be at least noninferior to LPN on the basis of clinical and oncologic outcomes, it is associated with a shorter learning curve, and this study showed no difference in overall cost when compared with HALPN. This suggests that RAPN may be an appropriate innovation to increase the adoption of NSS to patients in need.

Conclusions

In clinically similar groups of patients and tumors, operative costs were higher for RAPN largely because of robotic capital expenditures, while postoperative costs were higher for HALPN because of longer LOS. These cost differences offset each other, and no difference in total overall cost was found. Given comparable oncologic outcomes and patient safety, RAPN is a cost-efficient innovation that could increase the adoption of NSS.

Disclosure Statement

No competing financial interests exist.

Footnotes

Acknowledgments

Many thanks to Mark Hoffman, Stella Nelson, Linda Henning, Jeff Yardley, Jeremy Grimsley, and Susan Phillips for provision and interpretation of cost data. Work on this study was supported by the Integrated Cancer Information and Surveillance System (ICISS), UNC Lineberger Comprehensive Cancer Center with funding provided by the University Cancer Research Fund.

Abbreviations Used

References

Gill

, Aron

, Gervais

, Jewett

. Clinical practice. Small renal mass. N Engl J Med, 2010; 362:624–634.

Huang

, Levey

, Serio

et al. Chronic kidney disease after nephrectomy in patients with renal cortical tumours: A retrospective cohort study. Lancet Oncol, 2006; 7:735–740.

Lau

, Blute

, Weaver

et al. Matched comparison of radical nephrectomy vs nephron-sparing surgery in patients with unilateral renal cell carcinoma and a normal contralateral kidney. Mayo Clin Proc, 2000; 75:1236–1242.

Miller

, Schonlau

, Litwin

et al. Renal and cardiovascular morbidity after partial or radical nephrectomy. Cancer, 2008; 112:511–520.

Pettus

, Jang

, Thompson

et al. Effect of baseline glomerular filtration rate on survival in patients undergoing partial or radical nephrectomy for renal cortical tumors. Mayo Clin Proc, 2008; 83:1101–1106.

Thompson

, Boorjian

, Lohse

et al. Radical nephrectomy for pT1a renal masses may be associated with decreased overall survival compared with partial nephrectomy. J Urol, 2008; 179:468–473.

Miller

, Hollingsworth

, Hafez

et al.

Partial nephrectomy for small renal masses: An emerging quality of care concern?

J Urol, 2006; 175:853–858.

Miller

, Wei

, Dunn

, Hollenbeck

. Trends in the diffusion of laparoscopic nephrectomy. JAMA, 2006; 295:2480–2482.

Scherr

, Ng

, Munver

et al. Practice patterns among urologic surgeons treating localized renal cell carcinoma in the laparoscopic age: Technology versus oncology. Urology, 2003; 62:1007–1011.

10.

Benway

, Bhayani

. Robot-assisted partial nephrectomy: Evolution and recent advances. Curr Opin Urol, 2010; 20:119–124.

11.

Benway

, Bhayani

, Rogers

et al. Robot assisted partial nephrectomy versus laparoscopic partial nephrectomy for renal tumors: A multi-institutional analysis of perioperative outcomes. J Urol, 2009; 182:866–872.

12.

Deane

, Lee

, Box

et al. Robotic versus standard laparoscopic partial/wedge nephrectomy: A comparison of intraoperative and perioperative results from a single institution. J Endourol, 2008; 22:947–952.

13.

Lotan

. Economics of robotics in urology. Curr Opin Urol, 2010; 20:92–97.

14.

Bhayani

, Figenshau

. The Washington University Renorrhaphy for robotic partial nephrectomy: A detailed description of the technique displayed at the 2008 World Robotic Urologic Symposium. J Robot Surg, 2008; 2:139.

15.

Chughtai

, Abraham

, Finn

et al. Fast track open partial nephrectomy: Reduced postoperative length of stay with a goal-directed pathway does not compromise outcome. Adv Urol, 2008; 507543.

16.

Charlson

, Szatrowski

, Peterson

, Gold

. Validation of a combined comorbidity index. J Clin Epidemiol, 1994; 47:1245–1251.

17.

Kutikov

, Uzzo

. The R.E.N.A.L. nephrometry score: A comprehensive standardized system for quantitating renal tumor size, location and depth. J Urol, 2009; 182:844–853.

18.

Finkler

. The distinction between cost and charges. Ann Intern Med, 1982; 96:102–109.

19.

Janson

, Björholt

, Carlsson

et al. Randomized clinical trial of the costs of open and laparoscopic surgery for colonic cancer. Br J Surg, 2004; 91:409–417.

20.

Mihaylova

, Briggs

, O'Hagan

, Thompson

. Review of statistical methods for analysing healthcare resources and costs. Health Econ, 2011; 20:897–916.

21.

Thompson

, Barber

. How should cost data in pragmatic randomised trials be analysed? BMJ, 2000; 320:1197–1200.

22.

Nixon

, Thompson

. Parametric modelling of cost data in medical studies. Stat Med, 2004; 23:1311–1331.

23.

Mir

, Cadeddu

, Sleeper

, Lotan

. Cost comparison of robotic, laparoscopic, and open partial nephrectomy. J Endourol, 2011; 25:447–453.

24.

Wang

, Bhayani

. Robotic partial nephrectomy versus laparoscopic partial nephrectomy for renal cell carcinoma: Single-surgeon analysis of>100 consecutive procedures. Urology, 2009; 73:306–310.

25.

Scales

Jr , Jones

, Eisenstein

et al. Local cost structures and the economics of robot assisted radical prostatectomy. J Urol, 2005; 174:2323–2329.

26.

Mouraviev

, Nosnik

, Robertson

et al. Comparative financial analysis of minimally invasive surgery to open surgery for small renal tumours<or=3.5 cm: A single institutional experience. Eur Urol, 2007; 51:715–721.

27.

Park

, Pearle

, Cadeddu

, Lotan

. Laparoscopic and open partial nephrectomy: Cost comparison with analysis of individual parameters. J Endourol, 2007; 21:1449–1454.

28.

DeVoe

, Kercher

, Hope

et al. Hand-assisted laparoscopic partial nephrectomy after 60 cases: Comparison with open partial nephrectomy. Surg Endosc, 2009; 23:1075–1080.

29.

Porpiglia

, Volpe

, Billia

et al. Laparoscopic versus open partial nephrectomy: Analysis of the current literature. Eur Urol, 2008; 53:732–743.

30.

Bolenz

, Gupta

, Hotze

et al. Cost comparison of robotic, laparoscopic, and open radical prostatectomy for prostate cancer. Eur Urol, 2010; 57:453–458.

31.

Lotan

, Cadeddu

, Gettman

. The new economics of radical prostatectomy: Cost comparison of open, laparoscopic and robot assisted techniques. J Urol, 2004; 172:1431–1435.

Supplementary Material

Please find the following supplemental material available below.

For Open Access articles published under a Creative Commons License, all supplemental material carries the same license as the article it is associated with.

For non-Open Access articles published, all supplemental material carries a non-exclusive license, and permission requests for re-use of supplemental material or any part of supplemental material shall be sent directly to the copyright owner as specified in the copyright notice associated with the article.

0.00 MB

0.03 MB