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Keywords:

  • prostatectomy;
  • retropubic radical prostatectomy;
  • robot-assisted radical prostatectomy;
  • operative time;
  • prostate cancer

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Objectives

  • To determine factors that influence radical prostatectomy (RP) operative times.
  • Operative time assessment is inherent to defining surgeon learning curves and evaluating quality of care.

Subjects/Patients and Methods

  • Population-based observational cohort study using USA Surveillance, Epidemiology, and End Results (SEER)-Medicare linked data of men diagnosed with prostate cancer during 2003–2007 who underwent robot-assisted radical prostatectomy (RARP, 3458 men) and retropubic RP (RRP, 6993) through to 2009.
  • We obtained median operative time using anaesthesia administrative data for RP and used median regression to assess the contribution of patient, surgeon, and hospital factors to operative times.

Results

  • The median RARP operative time decreased from 315 to 247 min from 2003 to 2008–2009 (P < 0.001), while the median RRP operative time remained similar (195 vs 197 min, P = 0.90).
  • In adjusted analysis, RARP vs RRP (parameter estimate [PE] 70.9; 95% confidence interval [CI] 58, 84; P < 0.001) and obesity (PE 15; 95% CI 7, 23; P < 0.001) were associated with longer operative times while higher surgeon volumes were associated with shorter operative times (P < 0.001).
  • RPs performed by surgeons employed by group (parameter estimate [PE] –22.76; 95% CI –38, –7.49; P = 0.004) and non-government (PE –35.59; 95% CI –68.15, –3.03; P = 0.032) vs government facilities and non-profit vs government hospital ownership (PE –21.85; 95% CI –32.28, –11.42; P < 0.001) were associated with shorter operative times.

Conclusions

  • During our study period, RARP operative times decreased by 68 min while RRP operative times remained stagnant.
  • Higher surgeon volume was associated with shorter operative times, and selective referral or improved efficiency to the level of high-volume surgeons would net almost $15 million (USA dollars) in annual savings.

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Operative time as a performance metric has been described on several levels. The duration of an operation impacts its adoption by the surgical community. For example, laparoscopic radical prostatectomy (RP) was introduced in the early 1990s as a novel minimally invasive approach, yet there was little uptake in the USA due in part to excessive operative times of >9 h [1]. Once the operative time shortened to a more acceptable length of ≈3 h, the technique gained acceptance [2]. Similarly, operative time is commonly used to assess surgeon learning curves. As surgeons become more adept and skilled, the procedural duration decreases accordingly [3]. Operative time additionally has important implications for controlling costs and is used as an indicator of efficiency and as a focus for quality improvement initiatives [4, 5]. One minute of operating room time is estimated to cost in excess of $15 (USA dollar) [6]. While it has been shown that robot-assisted RP (RARP) is a significantly more costly than retropubic RP (RRP), largely due to fixed overhead costs, it has been shown that as the duration of RARP operative time decreases, so do overall costs [4]. Furthermore, operative time has been used to evaluate quality of care, as longer operations have demonstrated an increased risk of postoperative complications for both non-prostate surgery and robot-assisted urological surgery [7, 8]. Identifying factors that affect length of operative time for RARP and RRP has important implications for surgical training, cost, and quality of care.

While RP operative time has been reported in single-surgeon and single-institution series, evaluation beyond these settings is lacking, and little is known about RP operative times in the community. The purpose of the present population-based study was to characterise factors that affect RP operative times [9].

Subjects/Patients and Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Our study was exempted by the University of California, Los Angeles Institutional Review Board. Patient data were de-identified and the requirement for consent was waived. We used Surveillance, Epidemiology, and End Results (SEER)-Medicare data for analysis, which are composed of a linkage of population-based cancer registry data from 16 SEER areas covering ≈28% of the USA population with Medicare administrative data [10].

Study Cohort

We identified 19 914 men diagnosed with localised prostate cancer between 2003 and 2007 who underwent RRP or RARP through to 2009, based on the presence of Current Procedural Terminology, Fourth Edition (CPT-4) codes 55 866 for RARP and 55 840, 55 842, and 55 845 for RRP consistent with prior methods [11]. We excluded 2203 men who were not continuously enrolled in Medicare Part A and B or who were enrolled in health maintenance organisations (HMO) during the study period. We excluded 3449 men with missing data from their Medicare anaesthesia physician claims and 3811 men missing tumour registry information, resulting in a study cohort of 10 451 men who underwent RARP (3458) and RRP (6993).

Independent Variables

Information on patient age and year of operation was obtained from Medicare file. Comorbidity as measured by Klabunde modification of the Charlson score was derived from inpatient, outpatient, and carrier claims during the year before surgery [12]. Race/ethnicity, census measures of median household income and education, population density (non-metropolitan vs metropolitan), USA Census region, marital status, and National Cancer Institute (NCI) designation were obtained from SEER. Obesity was identified by International Classification of Diseases, 9th Edition (ICD-9) diagnosis codes V854, 278.00 and 278.01. We determined surgeon and hospital volume by aggregating the total number of RPs performed during the study period and categorising into quartiles. Surgeon age, practice type (government employment vs nongovernment solo, nongovernment two person practice, and nongovernment group [more than two urologists] practice), and academic and government hospital affiliation were determined by linking unique physician identifier numbers (UPIN) to the American Medical Association Masterfile.

Operative time was derived from a validated method using anaesthesia claims data [9]. Additional anaesthesia procedures were identified using the following Current Procedural Terminology (CPT)-4 codes: placement of epidural 62318, 62319, 62310, 62311, 62350; arterial line 36620; central venous catheter (CVC) 93593. Pelvic lymph node dissections (LNDs) were identified using CPT codes 55842 and 55845 for open RRP and 38571 for robotic LND.

Estimation of Cost Savings

We obtained the number of RPs performed during the year 2007 within each quartile of surgeon volumes from low to very high. We summed the product of surgeon volume parameter estimates and the number of RPs performed by low-, intermediate-, and high-volume surgeons to calculate the minutes of operative time that may be avoided by referral to very-high-volume surgeons. This was multiplied by $15, the estimated cost of operative time per minute [6]. We then extrapolated to the general population by dividing by 0.28, because SEER represents ≈28% of the USA population [13], and then divided by 0.32, because ≈32% of men undergoing RP are older than 65 years [14]. Finally, we initially identified 19 914 men who underwent RP during the study period; however, almost half were excluded due to missing data and ineligibility based on HMO or Medicare enrolment. To apply these cost savings to this initial cohort, we divided the cost savings by the percentage excluded, or 0.52.

Statistical Analysis

Because the main outcome of interest operative time was heavily right skewed, we report median rather than mean operative times. The non-parametric Wilcoxon rank-sum (two sample) test adjusting for clustering at the surgeon level was used for bivariable analyses [15]. Median regression was used to determine the effect of patient, surgeon, and hospital characteristics on RP operative time [16].

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

During our study period, the median operative time for RARP decreased from 315 min in 2003 to 247 min in 2008–2009 (P < 0.001), while median RRP operative time remained relatively constant at 195 to 199 min (Fig. 1). White men had shorter RARP operative times (P = 0.023), while married men experienced shorter RARP (P = 0.012) and RRP (P = 0.020) operative times, respectively. Obesity was associated with longer RARP and RRP operative times by 14 and 7 min, respectively (both P < 0.001). Although moderately differentiated tumours were associated with shorter RRP operative times (P < 0.001), LND did not significantly lengthen RARP and RRP operative times. Additional anaesthesia procedures, such as placement of an arterial line, CVC, or other anaesthesia procedures lengthened RRP (P < 0.001); however, only placement of CVC lengthened RARP (P < 0.001). There was significant geographic variation in RRP operative times (P < 0.001) but not in RARP operative times.

figure

Figure 1. Operative time for RARP and RRP by year.

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Higher surgeon volumes were associated with shorter RARP and RRP (both P < 0.001). Likewise, higher hospital volumes were associated with shorter RARP and RRP (P < 0.001 and P = 0.006, respectively). Additionally, surgeons in a group practice had shorter RARP and RRP operative times (both P < 0.001) than those in other practice types. Moreover, RARP duration in teaching hospitals was 54 min longer (P < 0.001) than that in non-teaching hospitals. In terms of NCI designation, RARP were shortest when performed in NCI designated Comprehensive Cancer Centres (235 min, P < 0.001); however, RRP were shortest when performed in centres without NCI designation (190 min, P < 0.001; Table 1).

Table 1. The median operative time (min) by surgical approach (RARP vs RRP) based on patient, tumour, hospital, and surgeon characteristics
VariableRARP, minPRRP, minP
No. patients3458 6993 
Patient    
Year:    
2003315<0.0011950.907
2004276 194 
2005264 196 
2006259 195 
2007259 199 
2008247 197 
Age at diagnosis, years:    
65–692640.6361960.766
70–74260 195 
≥75260 192 
Race:    
White2590.0231950.234
Black286 195 
Hispanic278 202 
Asian261 210 
Other250 195 
Marital status    
not married2740.0122020.019
married260 195 
unknown267 199 
Education level (% achieving high school degree)    
<752790.0611930.580
75–84.99263 196 
85–89.99265 198 
≥90258 195 
unknown290 161 
Median income (USA dollars, $)    
<35 0002670.3751940.231
35–44 999270 194 
45–59 999257 195 
≈60 000259 202 
unknown290 161 
Charlson score:    
02610.5211950.499
1269 195 
2+258 200 
unknown272 198 
Obesity:    
no261<0.001195<0.001
yes286 211 
Tumour    
Clinical stage:    
T12570.0291960.047
T2270 194 
T3/T4282 213 
unknown294 189 
Grade:    
well differentiated2390.485207<0.001
moderately differentiated266 192 
poorly differentiated/undiff.261 199 
unknown260 215 
Hospital    
Geographic regions:    
Northeast2790.630213<0.001
South249 181 
Midwest259 193 
West263 198 
Population density:    
Non-metropolitan2500.3871900.297
Metropolitan264 196 
NCI:    
no274<0.001190<0.001
clinical375 265 
comprehensive235 231 
Ownership:    
non-profit2570.06441940.111
proprietary273 193 
government301 209 
Teaching:    
no225<0.0011950.112
yes279 201 
Hospital volume:    
low295<0.0012060.006
intermediate280 197 
high275 193 
very high220 189 
Surgeon    
Surgeon volume:    
low310<0.001217<0.001
intermediate292 202 
high253 193 
very high221 177 
Surgeon's age, years    
<502730.2191961.000
≥50250 195 
Group:    
solo/2-person practice290<0.001196<0.001
group259 187 
medical school329 229 
non-government212 238 
government276 226 
undefined274 205 
Other    
LND:    
no LND2680.2161960.473
limited258 207 
openN/A 195 
Epidural:    
no2620.4391950.069
yes330201
A_line:    
no2680.416189<0.001
yes251235
CVC:    
no262<0.001194<0.001
yes356235
Any extra:    
no2670.398187<0.001
yes252216

In adjusted analyses, RARP operative times were longer than RRP (parameter estimate [PE] 70.9, 95% CI 57.64,84.15, P < 0.001). Additionally, obese men had longer operative times (PE 15.23; 95% CI 7.03, 23.43; P < 0.001), and any additional anaesthesia procedure added a median of 22.4 min (PE 22.4; 95% CI 15.93, 28.86, P < 0.001). There continued to be significant geographic variation, with shorter operative times in the South (PE –21.68, 95% CI –32.84, –10.52, P < 0.001) and Midwest (PE –16.34, 95% CI –25.62, –7.07, P < 0.001) vs the West. ‘Very high’, ‘high’, and ‘intermediate’ vs ‘low’ surgeon volume were associated with shorter operative times (PE –42.43; 95% CI –53.3, –31.55; P < 0.001, PE –26.04; 95% CI –35.4, –16.68; P < 0.001, and PE –10.6; 95% CI –18.66, –2.53; P = 0.010, respectively), and group practices and non-government vs government employment were associated with shorter operative times (PE –22.76, 95% CI –38.03, –7.49; P = 0.004, and PE –35.59, 95% CI –68.15, –3.03; P = 0.032). Non-profit ownership was associated with shorter operative times, compared with government ownership (PE –21.85, 95% CI –32.28, –11.42; P < 0.001). Finally, teaching status did not affect RP operative times (PE 3.19, 95% CI –8.52, 14.9, P = 0.593; Table 2).

Table 2. Overall cohort on adjusted analysis
VariableCategoryPELower CLUpper CLP
  1. CL, confidence limit; PX, procedure.

Surgeon's age 0.37–0.030.760.068
Age at diagnosis –1.10–4.041.850.465
Surgeon volume (Ref. Low)Intermediate–10.60–18.66–2.530.010
High–26.04–35.40–16.68<0.001
Very high–42.43–53.30–31.55<0.001
Hospital volume (Ref. Low)Intermediate–2.03–10.676.610.646
High1.84–9.9313.610.760
Very high–8.93–23.105.250.217
Year of RP (Ref. 2008)200315.774.6726.880.005
200413.973.8524.090.007
200513.443.1823.690.010
200613.814.9322.700.002
20078.60–0.4317.640.062
Geography regions (Ref. West)1 = Northeast0.32–12.6513.280.962
2 = South–21.68–32.84–10.52<0.001
3 = Midwest–16.34–25.62–7.07<0.001
Clinical stage (Ref. T3/T4)T1–2.52–14.969.920.691
T2–2.93–15.339.470.644
Grade (Ref. Poorly differentiated)1 = moderately–3.50–7.930.920.121
NCI (Ref. No)Clinical50.9429.3772.51<0.001
Comprehensive–10.75–27.435.920.206
Group (Ref. Government)Solo/2 person practice–11.40–29.556.750.218
Group–22.76–38.03–7.490.004
Medical school20.09–0.0440.220.051
Non-government–35.59–68.15–3.030.032
Ownership (Ref. Government)Non-profit–21.85–32.28–11.42<0.001
Proprietary–13.05–28.001.900.087
Teaching (Ref. No)Yes3.19–8.5214.900.593
Obesity (Ref. No)Yes15.237.0323.43<0.001
Any extra anaesthesia PX (Ref. No)Yes22.4015.9328.86<0.001
LND (Ref. Open)No3.04–6.2312.310.521
Limited0.70–12.4413.830.917
Surgical approach (Ref. RRP)RARP70.9057.6484.15<0.001

Finally, if all RPs were performed by very-high-volume surgeons in 2007, 46 574.6 min would be potentially avoided in our SEER-Medicare study, leading a cost saving of $698 619. Extrapolating nationally to RP regardless of age, savings of $14 994 398.17 may be achieved annually by selective referral or improved efficiency to the level of very-high-volume surgeons.

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Since attaining Food and Drug Administration approval in 2001, RARP has become the most popular approach to RP, comprising more than half of all RPs in 2008, edging out the ‘gold standard’ RRP [17]. As new surgical technologies are disseminated, the ability to identify factors that influence the length of the operation has important implications for understanding surgeon learning curves, determining quality of care, and estimating the financial impact of these new technologies. For instance, single centre series have reported learning curves for adoption of the robotic technique [18]. Moreover, a multi-centre study showed that RARP was associated with less variance and range in operative time than RRP [19]. However, outcomes beyond published high-volume centres are sparse [17].

The present study has several important findings. First, by using a validated method of determining actual operating room times by using anaesthesia claims data [10], we found that the median RARP vs RRP operative time was 71 min longer. While expert RARP surgeons have reported operative times shorter than RRP [20], the flattening out of individual surgeon's learning curve for RARP operative times may take more than 700 cases [21]. The present population-based finding that the robotic approach takes over an hour longer suggests that there may be opportunities for shortening RARP. Notably, during the study period from 2003 to 2009, operative times for RARP decreased annually, while the operative time for RRP remained constant. This probably reflects advances along the learning curve for RARP on a community level, as this mirrors the national increase in use of the robotic technique. This implies that as surgeons gain more experience with this technology, the median operative times progressively decrease. In contrast, RRP has not undergone any recent significant changes in technique, and the median operative times remained constant throughout the present study period. Improving the surgical efficiency of a new operation, such as RARP, may be achieved with greater dissemination of sound surgical technique and experience to lower volume surgeons. By providing collaborative feedback to lower volume surgeons, they may have the opportunity to progress faster along their learning curve, so that their efficiency approaches that of very-high-volume surgeons. Alternatively, selective referral to very-high-volume centres may encourage a shift of RARPs to centres with greater experience and shorter operative times.

Importantly, it has been suggested that as operative times decrease, so do overall costs. Scales et al. [4] showed that at high-volume hospitals where >10 RARPs were being performed weekly, RARP is cost equivalent to RRP and becomes even less expensive if the case volume exceeds 14 RARP/week. Thus, if RARP operative times shorten to allow more daily procedures, the cost of the robotic operation may be more competitive with its open counterpart.

Second, higher surgeon volume was associated with shorter RARP and RRP operative times. Similarly, higher surgeon volume is associated with fewer complications and shorter lengths of stay [22]. Cost savings for RP has also been shown for high-volume surgeons [23], and extrapolation of the present findings show that almost $15 million annually may be saved by shorter operative times achieved from selective referral to very-high-volume RP surgeons. Alternatively, these cost savings may also be attained if lower volume surgeons improve efficiency to match that of very-high-volume surgeons. Moreover, this figure does not factor in additional cost savings derived from the excess operating room capacity to perform additional procedures. To put this figure into context, the NCI allocated $19 million for prostate cancer research in 2011 [24].

Third, we identified obesity as an independent predictor of longer operative times, consistent with a study that showed patient preparation, control of the dorsal vascular complex, and performing nerve-sparing and the vesico-urethral anastomosis were longer in obese vs non-obese men [25]. The impact of obesity on operative time is particularly relevant given the rising incidence of obesity in the USA and its impact on exacerbating healthcare costs [26]. Additionally, obesity has been shown to adversely affect outcomes after RP, as it is associated with a greater risk of biochemical recurrence and castration-resistant disease after RP [27].

Fourth, we found that the type and location of a surgeon's practice influence operative time for RP. Surgeons in group or non-government practices had significantly shorter operating times than those employed by the government. Moreover, hospitals owned by the government had longer operative times than those that were owned by non-government entities. Interestingly, we also found that teaching hospital status did not have an impact on operative time. Additionally, there was significant geographic variation in RP operative times, consistent with prior studies that show significant geographical variation in RP use and outcomes [28].

The performance of LND during RP interestingly did not affect the length of the operation. Prior investigation revealed that significant variation exists between the number of LNs resected (extended vs limited) [29], and this may have a dampening effect on the added LND operative time.

The present study must be interpreted within the context of the study design. Our Medicare study includes only elderly men in which nerve-sparing may be performed with less frequency compared with younger men, and nerve-sparing technique, which we were unable to adjust for, may lengthen the operation. Additionally, the estimation of operative time was derived from anaesthesia claims data, which includes induction time. However, this methodology has been validated as a close approximation of procedure length [9]. Finally, recent findings from the National Surgical Quality Improvement Program show that RARP and RRP ‘set-up time’ are similar, and cancel out when estimating and comparing operative times [30].

In conclusion, operative times for RARP decreased over our contemporary study, while remaining stable for RRP; however, RARP was 71 min longer than RRP. Moreover, there was significant variation in RP operative times by geography, practice type and hospital ownership. Finally, higher RP surgeon volume was associated with shorter operative times and selective referral to efficient, high-volume surgeons nets significant cost savings due to shorter operative times alone.

Acknowledgements

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

This study used the linked SEER-Medicare database. The interpretation and reporting of these data are the sole responsibility of the authors. The authors acknowledge the efforts of the Applied Research Program, NCI; the Office of Research, Development and Information, CMS; Information Management Services (IMS), Inc.; and the SEER Program tumour registries in the creation of the SEER-Medicare database.

Conflict of Interest

  1. Top of page
  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References

Y.-C.S. reports paid consultancy work for MRI Advisory Board sponsored by Bayer and received institution funding from AHRQ; R01 (R01HS018535, R01 HS020263), and NCI; R21 (CA165092), outside the submitted work. No other authors declare any conflicts of interest.

References

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  2. Abstract
  3. Introduction
  4. Subjects/Patients and Methods
  5. Results
  6. Discussion
  7. Acknowledgements
  8. Conflict of Interest
  9. References
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Abbreviations
CPT

Current Procedural Terminology

CVC

central venous catheter

HMO

health maintenance organisations

LN(D)

lymph node (dissection)

PE

parameter estimate

NCI

National Cancer Institute

(RA)(R)RP

(robot-assisted) (retropubic) radical prostatectomy

SEER

Surveillance, Epidemiology, and End Results