REVIEW URRENT C OPINION
Relationship between surgical volume and outcomes in nephron-sparing surgery Benoit Peyronnet, Jean-Philippe Couapel, Jean-Jacques Patard, and Karim Bensalah
Purpose of review Provider volume has been shown to affect outcomes of various surgical procedures. Because of its technical complexity, it is likely that partial nephrectomy outcomes can be affected by hospital and/or surgeon volume. However, until recently, there were few publications on the subject. Our objective is to discuss recent findings on the impact of surgical volume on partial nephrectomy outcomes. Recent findings Two studies found a link between the number of partial nephrectomy performed at an institution and postoperative outcomes. Data extrapolated from articles on learning curve of laparoscopic partial nephrectomy suggest that surgeon volume can also affect partial nephrectomy outcomes. Partial nephrectomy is underused in low-volume centers. Robotic partial nephrectomy has a shorter learning curve compared to laparoscopic partial nephrectomy and may increase the use of partial nephrectomy vs. radical nephrectomy. Results on the impact of provider volume on the surgical approach are conflicting. Summary There are few publications suggesting an impact of hospital volume on partial nephrectomy outcomes but the importance of the surgeon volume remains unclear. Higher surgical volume is associated with increased use of partial nephrectomy. Keywords hospital volume, outcome, partial nephrectomy, robotic, surgeon volume
INTRODUCTION Forty years ago, Luft et al. [1] was the first one to evaluate the impact of volume on outcomes after various surgical procedures. Since then, many studies have investigated the relationship between provider volume and surgical outcomes [2]. In the late 1990s, urologists started to study this volume–outcome relationship for three major urological procedures: radical prostatectomy, cystectomy, and radical nephrectomy. Results were interesting but conflicting, particularly, for renal surgery [3]. Partial nephrectomy has become the standard treatment of localized renal masses [4]. Because of its technical complexity, it is likely that partial nephrectomy surgical outcomes can be affected by hospital and/or surgeon volume. The widespread use of partial nephrectomy took place recently, and until the past few years, there was little evidence concerning the impact of volume on partial nephrectomy outcomes. The objective of this article is to review and summarize current evidence of the volume–outcome relationship concerning partial nephrectomy.
VOLUME–OUTCOME RELATIONSHIP IN SURGERY Surgical volume can be appraised by two distinct factors that affect outcomes independently [5]: surgeon volume, that is, the number of procedures performed by a single surgeon in a year, and hospital volume, that is, the number of specific procedures performed in a year at a single institution. The impact of surgeon or hospital volume varies widely according to the procedure. Some interventions require limited resources beyond surgeon’s skills (e.g., laparoscopic prostatectomy), whereas others (e.g., caval thrombectomy) necessitate optimal collaboration of a broad range of resources such Department of Urology, Rennes University Hospital, University of Rennes, Rennes, France Correspondence to Professor Karim Bensalah, Department of Urology, Rennes University Hospital, University of Rennes, CHU Rennes, 2 rue Henri le Guilloux, 35000 Rennes, France. Tel: 00 33679608027; e-mail: [email protected] Curr Opin Urol 2014, 24:453–458 DOI:10.1097/MOU.0000000000000083
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Nephron-sparing surgery for renal cancers
KEY POINTS • There is limited data on surgical volume and partial nephrectomy outcomes. • Partial nephrectomy performed at high-volume institutions have lower complication rates and shorter length of hospital stay. • The use of partial nephrectomy increases at high-volume institutions compared to low-volume hospitals. • Articles on learning curve suggest that surgeons with higher volume of partial nephrectomy have less complications and diminished ischemia time. • Additional evidence is needed to better address the partial nephrectomy volume–outcome relationship.
Although there is no clear explanation to this relationship, two hypotheses have been formulated: ‘practice makes perfect’ – surgeons develop more skills as they treat more patients – and ‘selective referral’ – surgeons who achieve better results receive more referrals and, therefore, have higher volumes [5,6]. Because of this potential link between volume and outcomes, some purchasers and consumer groups have advocated selective referral of patients to high-volume providers, particularly, for high-risk surgeries [7]. In the USA, it has been suggested that this selective referral could prevent a significant number of deaths [8].
IMPACT OF VOLUME ON PARTIAL NEPHRECTOMY OUTCOMES
as an experienced anesthesia staff, specialized ICUs, or trained nursing teams. The two factors (surgeon and/or hospital volume) have rarely been simultaneously studied. Most published studies evaluated either surgeon or hospital volume. However, when considered as independent variables, it seems that the volume of an individual surgeon has a greater influence on outcome than the hospital volume [2,5]. Numerous reports proved that surgical volume affects outcomes [1–3,5,6]. The most striking evidence was found for high-risk surgical procedures such as pancreatic cancer surgery, pediatric cardiac surgery, or abdominal aortic aneurysm repair [2,5]. The impact of volume was less important for more common procedures such as carotid endarterectomy or coronary artery bypass [2,5].
Surgical mortality has been chosen as a surrogate marker of quality for many surgical procedures. However, it is not well suited for partial nephrectomy because death is a rare event [9 ,10 ]. Therefore, studies evaluating the volume–outcome issue for partial nephrectomy focused mainly on surgical outcomes such as complications, rate of positive surgical margins, or length of hospital stay. There is limited published data concerning partial nephrectomy. To date, only two studies have addressed the issue of volume–outcome relationship for partial nephrectomy [9 ,10 ]. Key findings of these two studies are summarized in Table 1. The first study is a retrospective analysis of a large administrative database (Nationwide Inpatient Sample) that collects patients’ discharge data from 20% of US community hospitals [9 ]. This analysis &&
&&
&&
&&
&&
P < 0.001
60%
55% 50%
50%
44%
40%
30% P < 0.001
P < 0.001
20%
17% 17% 12%
10%
15%
P = 0.05
10% 9%
1%
0% Blood transfusion
Postoperative complication
Low volume
LOS ≥ 5 days
Intermediate volume
1%
1%
In-hospital mortality
High volume
FIGURE 1. Partial nephrectomy outcomes according to hospital nephrectomy volume [9 ]. &&
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1% 0% P ¼ 0.5 16% 17%
Medium: 6–15 Low: 5 –
&&
P < 0.004*
Overall 14% PN + RN per year High: ³16 Retrospective/based on administrative database (NIS) Sun et al. [9 ]
8671
10.1% 15.1% 10.9% P = 0.02* High: 10–18 Medium: 5–9 Low: 4 –
NIS, Nationwide Inpatient Sample; PN, partial nephrectomy; RN, radical nephrectomy. *, statitically significant (P < 0.05).
47% 49% P < 0.001* – – –
– – –
Rate 0% At least 5 days 42% Rate –
Minute –
0.5% 0% 0% P ¼ 0.82 8.5 9.2 9 P = 0.001* 8% 16% 7% P ¼ 0.06 10.6% 15.1% 8.7% P ¼ 0.42
18 20 22 P = 0.02*
Rate 1.1% Minute 20 Days 7.6 Rate 6% Surgical 8.6% Medical 4.9% PN per year Very high: ³19 Prospective/based on medical records &&
Couapel et al. [10 ]
570
Complications Hospital volume categorization Number of PN Study design Study
Table 1. Impact of hospital volume on partial nephrectomy outcomes
Positive surgical margins
Length of stay
Warm ischemia time
Mortality
Relationshi p between surgical volume and outcomes Peyronnet et al.
included all kidney cancer surgeries (radical nephrectomy and partial nephrectomy) performed between 1998 and 2007, that is, 48 172 patients. Three categories of hospitals were considered according to the number of nephrectomies performed in a year: low volume (or less than 5 cases), intermediate volume (between 6 and 15 cases), and high volume (at least 16 cases). The authors concentrated their analysis on a subgroup of patients with partial nephrectomy and found that high-volume institutions had lower blood transfusion rates, decreased complication rates, and diminished length of hospital stay, whereas mortality did not differ significantly (Table 1; Fig. 1). Although data on warm ischemia time and positive surgical margins were missing, these results suggested a positive link between hospital volume and partial nephrectomy surgical outcomes. The second publication is the National Observational Registry on the Practice and Hemostasis in Partial Nephrectomy (NEPHRON) study, which is a French multicentric prospective observational study that collected data from all patients with a renal tumor managed by partial nephrectomy or radical nephrectomy over a period of 6 months [10 ]; 570 cases of partial nephrectomy from 56 centers (public and private, academic, and nonacademic) were included. Institutions were divided into four quartiles according to the number of partial nephrectomy performed during the 6-month study period (low: 4; moderate: 5–9; high: 10–18; very high: ³19). The authors found that volume affected length of hospital stay, warm ischemia time, medical complications, and hemoglobin decrease, all that favored high-volume institutions. However, there was no significant difference in terms of surgical complications and operative time (Table 1). Although it did not reach significance, there was a trend toward an impact of volume on the positive surgical margins rate, which was highest (16%) at moderate-volume institutions. Interestingly, the largest differences were not observed between the very high and the low-volume groups; worse outcomes were seen in the moderate-volume group with a 15% rate of medical and surgical complications and a mean length of stay of 9 days (Table 1). A possible explanation was that the use of laparoscopic partial nephrectomy (LPN), which is known to be a difficult operation that requires a long learning curve to be mastered, was more frequent in this moderate group. The main limitation of these two studies is that surgeon volume was not taken into account, whereas numerous reports have suggested that it could have a greater influence than hospital volume on surgical outcomes [2].
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&&
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Nephron-sparing surgery for renal cancers 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Low RNS
All tumors
Intermediate
High RNS
FIGURE 2. Proportion of tumors treated with partial nephrectomy by surgeons according to low – fewer than 5 (light gray bars); intermediate – 5–20 (gray bars), and high – greater than 20 per year (black bars) annual renal surgical volume and renal nephrometry score [14 ]. &
IMPACT OF VOLUME ON THE USE OF PARTIAL NEPHRECTOMY Partial nephrectomy provides similar oncological outcomes to that of radical nephrectomy and better preserves renal function. As such, partial nephrectomy has become the standard treatment of renal masses smaller than 7 cm [4]. Despite these proven benefits, partial nephrectomy remains widely underused [11]. Many studies tried to correlate hospital and/or surgeon volume to the frequency of use of partial nephrectomy. Most of these publications showed that the use of partial nephrectomy greatly depended on both hospital and surgeon volume [9 ,10 ,12 ,13,14 ,15,16,17 ]. Abouassaly et al. [16] analyzed data from a Canadian administrative database of 24 579 patients who had surgery for a renal mass. Surgeons and hospitals were divided into four quartiles according to their volume. The ratio of partial nephrectomy vs. radical nephrectomy increased with both surgeon (10.9 vs. 24.7% for low and high-volume surgeons, respectively) and hospital volumes (9.9 vs. 22.7% for low and high-volume hospitals, respectively) (Fig. 2). In the NEPHRON study [10 ], there was a similar trend: centers with higher volumes had an increased ratio of partial nephrectomy vs. radical nephrectomy (40 vs. 55% in low and high-volume institutions, respectively). &&
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Two studies further explored differences in the use of partial nephrectomy according to the surgical volume. Lane et al. [14 ] used a clinical database of 1433 patients from three American centers surgically treated for a renal tumor. They found that the association between surgeon volume and the use of partial nephrectomy concerned only intermediate and highly complex renal tumors (renal nephrometry score ³ 7) with no difference observed in the subset of tumors of low complexity (renal nephrometry score 6). Based on a survey sent to 764 urologists, Weight et al. [15] drew similar conclusions. &
IMPACT OF VOLUME ON SURGICAL APPROACH There is little evidence on whether surgical volume influences the choice of the surgical approach for partial nephrectomy. In the NEPHRON study, the use of robotic partial nephrectomy (RPN) increased with center volume [10 ], and moderate-volume institutions (between 10 and 18 partial nephrectomy per year) had the highest rates of LPN use (39.2 vs. 19.1, 12.8, and 21.7% in the low, high, and very highvolume groups, respectively; P < 0.001) (Fig. 3). The authors hypothesized that it could explain the worse surgical outcomes observed in this group. Conversely, in a retrospective cohort of 48 384 patients from an administrative database, higher &&
Volume 24 • Number 5 • September 2014
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Relationshi p between surgical volume and outcomes Peyronnet et al. 80
Proportion of patients (%)
60
74.5
72.1
70
Surgical approach 58.8
OPN 51.4
50
LPN RALPN
39.2
40
p < 0.001 30 20
21.7 19.5
19.1 12.8
15.1 9.5
10 0
Very high
High
Moderate
6.4 Low
FIGURE 3. Surgical approach according to hospital partial nephrectomy volume [10 ]. &&
nephrectomy volume was associated with an increased use of LPN in multivariate analysis (odds ratio ¼ 1.09; P < 0.0001) [13]. However, there was no distinction between LPN and RPN, so we do not know which approach was more commonly used. Recent reports suggested that the development of laparoscopy could have decreased the use of partial nephrectomy, many urologists favoring laparoscopic radical nephrectomy over open partial nephrectomy (because of its perceived high morbidity) or LPN (because of its technical complexity) [18]. Two recently published studies found that the presence of robotic technology at an institution was associated with higher ratios of partial nephrectomy vs. radical nephrectomy [12 ,17 ]. RPN is less technically demanding than LPN and could lead urologists of lowvolume centers to increase their use of partial nephrectomy.
and confirmed that LPN is a technically challenging surgical procedure that requires a long learning curve to reach optimal surgical outcomes [19–21]. RPN has become a widely used procedure, and four recent publications suggest that it is associated with a shorter learning curve [21–23]. In a singlesurgeon series comparing the first 100 LPN and the first 50 RPN [21], the authors noted improvements in operative time, ischemia time, and blood loss with increasing LPN experience whereas no progress was seen between early and late experience in the RPN group. Most of these findings imply that outcomes improve with growing surgeon experience, especially for LPN. This might indicate that surgeon volume is associated with better partial nephrectomy outcomes.
LEARNING CURVE ISSUE
CONCLUSION
The volume–outcome and the learning curve issues have usually been addressed separately in the literature [2]. There is limited data on the learning curve of open partial nephrectomy. The vast majority of the publications concern LPN and RPN. In a singlesurgeon series of 800 consecutive LPN, Gill et al. [19] showed that complications and warm ischemia time diminished with increasing experience. However, for them it took more than 200 cases to decrease the complication rate below 20% and 500 cases to diminish mean ischemia time below 30 min. Of interest, in the latest era – where the best outcomes were obtained – their annual volume of LPN had greatly increased (from 64 to 134 procedures per year) suggesting that both volume and learning curve could have played a role on their improved results. Other publications supported these findings
The association between volume and surgical outcomes has been addressed for many surgical procedures and there is usually a positive link between higher institution and/or surgeon volume and optimal surgical outcomes. In the field of urology, the volume–outcome relationship has been mainly analyzed for radical prostatectomy. There are limited data concerning partial nephrectomy. Published studies hint at a relationship between the number of partial nephrectomy performed by an institution and better postoperative outcomes, such as decreased complications and/or length of stay. High-volume institutions also have a higher partial nephrectomy vs. radical nephrectomy ratio. The impact of volume on positive surgical margins rate and warm ischemia time is less clear.
&
&
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Nephron-sparing surgery for renal cancers
The only data we have concerning surgeon volume are extrapolated from articles on learning curve of LPN; these suggest that high-volume surgeons have better results. However, RPN has become a widely used procedure and could have a shorter learning curve. There is a need for additional prospective studies to better evaluate this issue.
Acknowledgements None. Conflicts of interest There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the period of review, have been highlighted as: & of special interest && of outstanding interest 1. Luft HS, Bunker JP, Enthoven AC. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med 1979; 301: 1364–1369. 2. Chowdhury MM, Dagash H, Pierro A. A systematic review of the impact of volume of surgery and specialization on patient outcome. Br J Surg 2007; 94: 145–161. 3. Nuttall M, van der Meulen J, Phillips N, et al. A systematic review and critique of the literature relating hospital or surgeon volume to health outcomes for 3 urological cancer procedures. J Urol 2004; 172(6 Pt 1):2145–2152. 4. Ljungberg B, Bensalah K, Bex A, et al. Guidelines on renal cell carcinoma. Uroweb 2013. http://www.uroweb.org/gls/pdf/10_Renal_Cell_Carcinoma_LRV2.pdf [Accessed 27 March 2014]. 5. Halm EA, Lee C, Chassin MR. Is volume related to outcome in health care? A systematic review and methodologic critique of the literature. Ann Intern Med 2002; 137: 511–520. 6. Bentrem DJ, Brennan MF. Outcomes in oncologic surgery: does volume make a difference? World J Surg 2005; 29: 1210–1216. 7. Milstein A, Galvin RS, Delbanco SF, et al. Improving the safety of health care: the leapfrog initiative. Eff Clin Pract 2000; 3: 313. 8. Dudley R, Johansen K, Brand R, et al. Selective referral to high-volume hospitals: estimating potentially avoidable deaths. JAMA 2000; 283: 1159.
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9. Sun M, Bianchi M, Trinh QD, et al. Hospital volume is a determinant of postoperative complications, blood transfusion and length of stay after radical or partial nephrectomy. J Urol 2012; 187: 405–410. This is the first study that shows, based on data extracted from an administrative database, that hospital volume affect partial nephrectomy outcomes. 10. Couapel JP, Bensalah K, Bernhard JC, et al. Is there a volume-outcome relationship for partial nephrectomy. World J Urol 2013. [Epub ahead of && print] This is the first study based on a multicentric prospective clinical database to show an impact of hospital volume on surgical outcomes of partial nephrectomy. Worse outcomes were observed at moderate-volume institutions. 11. Dulabon LM, Lowrance WT, Russo P, et al. Trends in renal tumor surgery delivery within the United States. Cancer 2010; 116: 2316–2321. 12. Kardos SV, Gross CP, Shah ND, et al. Association of type of renal & surgery and access to robotic technology for kidney cancer: results from a population-based cohort. BJU Int 2014. [Epub ahead of print] This is the largest study to show that robotic technology is associated with an increased use of partial nephrectomy vs. radical nephrectomy, regardless of provider volume. 13. Poon SA, Silberstein JL, Chen LY, et al. Trends in partial and radical nephrectomy: an analysis of case logs from certifying urologists. J Urol 2013; 190: 464–469. 14. Lane BR, Golan S, Eggener S, et al. Differential use of partial nephrectomy for intermediate and high complexity tumors may explain variability in & reported utilization rates. J Urol 2013; 189: 2047–2053. A study that shows that the underuse of partial nephrectomy in low-volume centers only concerns complex tumors. 15. Weight CJ, Crispen PL, Breau RH, et al. Practice-setting and surgeon characteristics heavily influence the decision to perform partial nephrectomy among American Urologic Association surgeons. BJU Int 2013; 111: 731–738. 16. Abouassaly R, Finelli A, Tomlinson GA, et al. Volume-outcome relationships in the treatment of renal tumors. J Urol 2012; 187: 1984–1988. 17. Patel HD, Mullins JK, Pierorazio PM, et al. Trends in renal surgery: robotic technology is associated with increased use of partial nephrectomy. J Urol & 2013; 189: 1229–1235. A study that suggests that robotic technology is associated with an increased use of partial nephrectomy regardless of surgical volume. 18. Abouassaly R, Alibhai SM, Tomlinson G, et al. Unintended consequences of laparoscopic surgery on partial nephrectomy for kidney cancer. J Urol 2010; 183: 467. 19. Gill IS, Kamoi K, Aron M, et al. 800 Laparoscopic partial nephrectomies: a single surgeon series. J Urol 2010; 183: 34–41. 20. Porpiglia F, Bertolo R, Amparore D, et al. Margins, ischaemia and complications rate after laparoscopic partial nephrectomy: impact of learning curve and tumour anatomical characteristics. BJU Int 2013; 112: 1125–1132. 21. Pierorazio PM, Patel HD, Feng T, et al. Robotic-assisted versus traditional laparoscopic partial nephrectomy: comparison of outcomes and evaluation of learning curve. Urology 2011; 78: 813–819. 22. Haseebuddin M, Benway BM, Cabello JM, et al. Robot-assisted partial nephrectomy: evaluation of learning curve for an experienced renal surgeon. J Endourol 2010; 24: 57–61. 23. Mottrie A, De Naeyer G, Schatteman P, et al. Impact of the learning curve on perioperative outcomes in patients who underwent robotic partial nephrectomy for parenchymal renal tumours. Eur Urol 2010; 58: 127– 132. &&
Volume 24 • Number 5 • September 2014
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Relationship between surgical volume and outcomes in nephron-sparing surgery Benoit Peyronnet, Jean-Philippe Couapel, Jean-Jacques Patard, and Karim Bensalah
Purpose of review Provider volume has been shown to affect outcomes of various surgical procedures. Because of its technical complexity, it is likely that partial nephrectomy outcomes can be affected by hospital and/or surgeon volume. However, until recently, there were few publications on the subject. Our objective is to discuss recent findings on the impact of surgical volume on partial nephrectomy outcomes. Recent findings Two studies found a link between the number of partial nephrectomy performed at an institution and postoperative outcomes. Data extrapolated from articles on learning curve of laparoscopic partial nephrectomy suggest that surgeon volume can also affect partial nephrectomy outcomes. Partial nephrectomy is underused in low-volume centers. Robotic partial nephrectomy has a shorter learning curve compared to laparoscopic partial nephrectomy and may increase the use of partial nephrectomy vs. radical nephrectomy. Results on the impact of provider volume on the surgical approach are conflicting. Summary There are few publications suggesting an impact of hospital volume on partial nephrectomy outcomes but the importance of the surgeon volume remains unclear. Higher surgical volume is associated with increased use of partial nephrectomy. Keywords hospital volume, outcome, partial nephrectomy, robotic, surgeon volume
INTRODUCTION Forty years ago, Luft et al. [1] was the first one to evaluate the impact of volume on outcomes after various surgical procedures. Since then, many studies have investigated the relationship between provider volume and surgical outcomes [2]. In the late 1990s, urologists started to study this volume–outcome relationship for three major urological procedures: radical prostatectomy, cystectomy, and radical nephrectomy. Results were interesting but conflicting, particularly, for renal surgery [3]. Partial nephrectomy has become the standard treatment of localized renal masses [4]. Because of its technical complexity, it is likely that partial nephrectomy surgical outcomes can be affected by hospital and/or surgeon volume. The widespread use of partial nephrectomy took place recently, and until the past few years, there was little evidence concerning the impact of volume on partial nephrectomy outcomes. The objective of this article is to review and summarize current evidence of the volume–outcome relationship concerning partial nephrectomy.
VOLUME–OUTCOME RELATIONSHIP IN SURGERY Surgical volume can be appraised by two distinct factors that affect outcomes independently [5]: surgeon volume, that is, the number of procedures performed by a single surgeon in a year, and hospital volume, that is, the number of specific procedures performed in a year at a single institution. The impact of surgeon or hospital volume varies widely according to the procedure. Some interventions require limited resources beyond surgeon’s skills (e.g., laparoscopic prostatectomy), whereas others (e.g., caval thrombectomy) necessitate optimal collaboration of a broad range of resources such Department of Urology, Rennes University Hospital, University of Rennes, Rennes, France Correspondence to Professor Karim Bensalah, Department of Urology, Rennes University Hospital, University of Rennes, CHU Rennes, 2 rue Henri le Guilloux, 35000 Rennes, France. Tel: 00 33679608027; e-mail: [email protected] Curr Opin Urol 2014, 24:453–458 DOI:10.1097/MOU.0000000000000083
0963-0643 ã 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins
www.co-urology.com
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Nephron-sparing surgery for renal cancers
KEY POINTS • There is limited data on surgical volume and partial nephrectomy outcomes. • Partial nephrectomy performed at high-volume institutions have lower complication rates and shorter length of hospital stay. • The use of partial nephrectomy increases at high-volume institutions compared to low-volume hospitals. • Articles on learning curve suggest that surgeons with higher volume of partial nephrectomy have less complications and diminished ischemia time. • Additional evidence is needed to better address the partial nephrectomy volume–outcome relationship.
Although there is no clear explanation to this relationship, two hypotheses have been formulated: ‘practice makes perfect’ – surgeons develop more skills as they treat more patients – and ‘selective referral’ – surgeons who achieve better results receive more referrals and, therefore, have higher volumes [5,6]. Because of this potential link between volume and outcomes, some purchasers and consumer groups have advocated selective referral of patients to high-volume providers, particularly, for high-risk surgeries [7]. In the USA, it has been suggested that this selective referral could prevent a significant number of deaths [8].
IMPACT OF VOLUME ON PARTIAL NEPHRECTOMY OUTCOMES
as an experienced anesthesia staff, specialized ICUs, or trained nursing teams. The two factors (surgeon and/or hospital volume) have rarely been simultaneously studied. Most published studies evaluated either surgeon or hospital volume. However, when considered as independent variables, it seems that the volume of an individual surgeon has a greater influence on outcome than the hospital volume [2,5]. Numerous reports proved that surgical volume affects outcomes [1–3,5,6]. The most striking evidence was found for high-risk surgical procedures such as pancreatic cancer surgery, pediatric cardiac surgery, or abdominal aortic aneurysm repair [2,5]. The impact of volume was less important for more common procedures such as carotid endarterectomy or coronary artery bypass [2,5].
Surgical mortality has been chosen as a surrogate marker of quality for many surgical procedures. However, it is not well suited for partial nephrectomy because death is a rare event [9 ,10 ]. Therefore, studies evaluating the volume–outcome issue for partial nephrectomy focused mainly on surgical outcomes such as complications, rate of positive surgical margins, or length of hospital stay. There is limited published data concerning partial nephrectomy. To date, only two studies have addressed the issue of volume–outcome relationship for partial nephrectomy [9 ,10 ]. Key findings of these two studies are summarized in Table 1. The first study is a retrospective analysis of a large administrative database (Nationwide Inpatient Sample) that collects patients’ discharge data from 20% of US community hospitals [9 ]. This analysis &&
&&
&&
&&
&&
P < 0.001
60%
55% 50%
50%
44%
40%
30% P < 0.001
P < 0.001
20%
17% 17% 12%
10%
15%
P = 0.05
10% 9%
1%
0% Blood transfusion
Postoperative complication
Low volume
LOS ≥ 5 days
Intermediate volume
1%
1%
In-hospital mortality
High volume
FIGURE 1. Partial nephrectomy outcomes according to hospital nephrectomy volume [9 ]. &&
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Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
1% 0% P ¼ 0.5 16% 17%
Medium: 6–15 Low: 5 –
&&
P < 0.004*
Overall 14% PN + RN per year High: ³16 Retrospective/based on administrative database (NIS) Sun et al. [9 ]
8671
10.1% 15.1% 10.9% P = 0.02* High: 10–18 Medium: 5–9 Low: 4 –
NIS, Nationwide Inpatient Sample; PN, partial nephrectomy; RN, radical nephrectomy. *, statitically significant (P < 0.05).
47% 49% P < 0.001* – – –
– – –
Rate 0% At least 5 days 42% Rate –
Minute –
0.5% 0% 0% P ¼ 0.82 8.5 9.2 9 P = 0.001* 8% 16% 7% P ¼ 0.06 10.6% 15.1% 8.7% P ¼ 0.42
18 20 22 P = 0.02*
Rate 1.1% Minute 20 Days 7.6 Rate 6% Surgical 8.6% Medical 4.9% PN per year Very high: ³19 Prospective/based on medical records &&
Couapel et al. [10 ]
570
Complications Hospital volume categorization Number of PN Study design Study
Table 1. Impact of hospital volume on partial nephrectomy outcomes
Positive surgical margins
Length of stay
Warm ischemia time
Mortality
Relationshi p between surgical volume and outcomes Peyronnet et al.
included all kidney cancer surgeries (radical nephrectomy and partial nephrectomy) performed between 1998 and 2007, that is, 48 172 patients. Three categories of hospitals were considered according to the number of nephrectomies performed in a year: low volume (or less than 5 cases), intermediate volume (between 6 and 15 cases), and high volume (at least 16 cases). The authors concentrated their analysis on a subgroup of patients with partial nephrectomy and found that high-volume institutions had lower blood transfusion rates, decreased complication rates, and diminished length of hospital stay, whereas mortality did not differ significantly (Table 1; Fig. 1). Although data on warm ischemia time and positive surgical margins were missing, these results suggested a positive link between hospital volume and partial nephrectomy surgical outcomes. The second publication is the National Observational Registry on the Practice and Hemostasis in Partial Nephrectomy (NEPHRON) study, which is a French multicentric prospective observational study that collected data from all patients with a renal tumor managed by partial nephrectomy or radical nephrectomy over a period of 6 months [10 ]; 570 cases of partial nephrectomy from 56 centers (public and private, academic, and nonacademic) were included. Institutions were divided into four quartiles according to the number of partial nephrectomy performed during the 6-month study period (low: 4; moderate: 5–9; high: 10–18; very high: ³19). The authors found that volume affected length of hospital stay, warm ischemia time, medical complications, and hemoglobin decrease, all that favored high-volume institutions. However, there was no significant difference in terms of surgical complications and operative time (Table 1). Although it did not reach significance, there was a trend toward an impact of volume on the positive surgical margins rate, which was highest (16%) at moderate-volume institutions. Interestingly, the largest differences were not observed between the very high and the low-volume groups; worse outcomes were seen in the moderate-volume group with a 15% rate of medical and surgical complications and a mean length of stay of 9 days (Table 1). A possible explanation was that the use of laparoscopic partial nephrectomy (LPN), which is known to be a difficult operation that requires a long learning curve to be mastered, was more frequent in this moderate group. The main limitation of these two studies is that surgeon volume was not taken into account, whereas numerous reports have suggested that it could have a greater influence than hospital volume on surgical outcomes [2].
0963-0643 ã 2014 Wolters Kluwer Health | Lippincott Williams & Wilkins
&&
www.co-urology.com
455
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
Nephron-sparing surgery for renal cancers 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Low RNS
All tumors
Intermediate
High RNS
FIGURE 2. Proportion of tumors treated with partial nephrectomy by surgeons according to low – fewer than 5 (light gray bars); intermediate – 5–20 (gray bars), and high – greater than 20 per year (black bars) annual renal surgical volume and renal nephrometry score [14 ]. &
IMPACT OF VOLUME ON THE USE OF PARTIAL NEPHRECTOMY Partial nephrectomy provides similar oncological outcomes to that of radical nephrectomy and better preserves renal function. As such, partial nephrectomy has become the standard treatment of renal masses smaller than 7 cm [4]. Despite these proven benefits, partial nephrectomy remains widely underused [11]. Many studies tried to correlate hospital and/or surgeon volume to the frequency of use of partial nephrectomy. Most of these publications showed that the use of partial nephrectomy greatly depended on both hospital and surgeon volume [9 ,10 ,12 ,13,14 ,15,16,17 ]. Abouassaly et al. [16] analyzed data from a Canadian administrative database of 24 579 patients who had surgery for a renal mass. Surgeons and hospitals were divided into four quartiles according to their volume. The ratio of partial nephrectomy vs. radical nephrectomy increased with both surgeon (10.9 vs. 24.7% for low and high-volume surgeons, respectively) and hospital volumes (9.9 vs. 22.7% for low and high-volume hospitals, respectively) (Fig. 2). In the NEPHRON study [10 ], there was a similar trend: centers with higher volumes had an increased ratio of partial nephrectomy vs. radical nephrectomy (40 vs. 55% in low and high-volume institutions, respectively). &&
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Two studies further explored differences in the use of partial nephrectomy according to the surgical volume. Lane et al. [14 ] used a clinical database of 1433 patients from three American centers surgically treated for a renal tumor. They found that the association between surgeon volume and the use of partial nephrectomy concerned only intermediate and highly complex renal tumors (renal nephrometry score ³ 7) with no difference observed in the subset of tumors of low complexity (renal nephrometry score 6). Based on a survey sent to 764 urologists, Weight et al. [15] drew similar conclusions. &
IMPACT OF VOLUME ON SURGICAL APPROACH There is little evidence on whether surgical volume influences the choice of the surgical approach for partial nephrectomy. In the NEPHRON study, the use of robotic partial nephrectomy (RPN) increased with center volume [10 ], and moderate-volume institutions (between 10 and 18 partial nephrectomy per year) had the highest rates of LPN use (39.2 vs. 19.1, 12.8, and 21.7% in the low, high, and very highvolume groups, respectively; P < 0.001) (Fig. 3). The authors hypothesized that it could explain the worse surgical outcomes observed in this group. Conversely, in a retrospective cohort of 48 384 patients from an administrative database, higher &&
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Relationshi p between surgical volume and outcomes Peyronnet et al. 80
Proportion of patients (%)
60
74.5
72.1
70
Surgical approach 58.8
OPN 51.4
50
LPN RALPN
39.2
40
p < 0.001 30 20
21.7 19.5
19.1 12.8
15.1 9.5
10 0
Very high
High
Moderate
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FIGURE 3. Surgical approach according to hospital partial nephrectomy volume [10 ]. &&
nephrectomy volume was associated with an increased use of LPN in multivariate analysis (odds ratio ¼ 1.09; P < 0.0001) [13]. However, there was no distinction between LPN and RPN, so we do not know which approach was more commonly used. Recent reports suggested that the development of laparoscopy could have decreased the use of partial nephrectomy, many urologists favoring laparoscopic radical nephrectomy over open partial nephrectomy (because of its perceived high morbidity) or LPN (because of its technical complexity) [18]. Two recently published studies found that the presence of robotic technology at an institution was associated with higher ratios of partial nephrectomy vs. radical nephrectomy [12 ,17 ]. RPN is less technically demanding than LPN and could lead urologists of lowvolume centers to increase their use of partial nephrectomy.
and confirmed that LPN is a technically challenging surgical procedure that requires a long learning curve to reach optimal surgical outcomes [19–21]. RPN has become a widely used procedure, and four recent publications suggest that it is associated with a shorter learning curve [21–23]. In a singlesurgeon series comparing the first 100 LPN and the first 50 RPN [21], the authors noted improvements in operative time, ischemia time, and blood loss with increasing LPN experience whereas no progress was seen between early and late experience in the RPN group. Most of these findings imply that outcomes improve with growing surgeon experience, especially for LPN. This might indicate that surgeon volume is associated with better partial nephrectomy outcomes.
LEARNING CURVE ISSUE
CONCLUSION
The volume–outcome and the learning curve issues have usually been addressed separately in the literature [2]. There is limited data on the learning curve of open partial nephrectomy. The vast majority of the publications concern LPN and RPN. In a singlesurgeon series of 800 consecutive LPN, Gill et al. [19] showed that complications and warm ischemia time diminished with increasing experience. However, for them it took more than 200 cases to decrease the complication rate below 20% and 500 cases to diminish mean ischemia time below 30 min. Of interest, in the latest era – where the best outcomes were obtained – their annual volume of LPN had greatly increased (from 64 to 134 procedures per year) suggesting that both volume and learning curve could have played a role on their improved results. Other publications supported these findings
The association between volume and surgical outcomes has been addressed for many surgical procedures and there is usually a positive link between higher institution and/or surgeon volume and optimal surgical outcomes. In the field of urology, the volume–outcome relationship has been mainly analyzed for radical prostatectomy. There are limited data concerning partial nephrectomy. Published studies hint at a relationship between the number of partial nephrectomy performed by an institution and better postoperative outcomes, such as decreased complications and/or length of stay. High-volume institutions also have a higher partial nephrectomy vs. radical nephrectomy ratio. The impact of volume on positive surgical margins rate and warm ischemia time is less clear.
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Nephron-sparing surgery for renal cancers
The only data we have concerning surgeon volume are extrapolated from articles on learning curve of LPN; these suggest that high-volume surgeons have better results. However, RPN has become a widely used procedure and could have a shorter learning curve. There is a need for additional prospective studies to better evaluate this issue.
Acknowledgements None. Conflicts of interest There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING Papers of particular interest, published within the period of review, have been highlighted as: & of special interest && of outstanding interest 1. Luft HS, Bunker JP, Enthoven AC. Should operations be regionalized? The empirical relation between surgical volume and mortality. N Engl J Med 1979; 301: 1364–1369. 2. Chowdhury MM, Dagash H, Pierro A. A systematic review of the impact of volume of surgery and specialization on patient outcome. Br J Surg 2007; 94: 145–161. 3. Nuttall M, van der Meulen J, Phillips N, et al. A systematic review and critique of the literature relating hospital or surgeon volume to health outcomes for 3 urological cancer procedures. J Urol 2004; 172(6 Pt 1):2145–2152. 4. Ljungberg B, Bensalah K, Bex A, et al. Guidelines on renal cell carcinoma. Uroweb 2013. http://www.uroweb.org/gls/pdf/10_Renal_Cell_Carcinoma_LRV2.pdf [Accessed 27 March 2014]. 5. Halm EA, Lee C, Chassin MR. Is volume related to outcome in health care? A systematic review and methodologic critique of the literature. Ann Intern Med 2002; 137: 511–520. 6. Bentrem DJ, Brennan MF. Outcomes in oncologic surgery: does volume make a difference? World J Surg 2005; 29: 1210–1216. 7. Milstein A, Galvin RS, Delbanco SF, et al. Improving the safety of health care: the leapfrog initiative. Eff Clin Pract 2000; 3: 313. 8. Dudley R, Johansen K, Brand R, et al. Selective referral to high-volume hospitals: estimating potentially avoidable deaths. JAMA 2000; 283: 1159.
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9. Sun M, Bianchi M, Trinh QD, et al. Hospital volume is a determinant of postoperative complications, blood transfusion and length of stay after radical or partial nephrectomy. J Urol 2012; 187: 405–410. This is the first study that shows, based on data extracted from an administrative database, that hospital volume affect partial nephrectomy outcomes. 10. Couapel JP, Bensalah K, Bernhard JC, et al. Is there a volume-outcome relationship for partial nephrectomy. World J Urol 2013. [Epub ahead of && print] This is the first study based on a multicentric prospective clinical database to show an impact of hospital volume on surgical outcomes of partial nephrectomy. Worse outcomes were observed at moderate-volume institutions. 11. Dulabon LM, Lowrance WT, Russo P, et al. Trends in renal tumor surgery delivery within the United States. Cancer 2010; 116: 2316–2321. 12. Kardos SV, Gross CP, Shah ND, et al. Association of type of renal & surgery and access to robotic technology for kidney cancer: results from a population-based cohort. BJU Int 2014. [Epub ahead of print] This is the largest study to show that robotic technology is associated with an increased use of partial nephrectomy vs. radical nephrectomy, regardless of provider volume. 13. Poon SA, Silberstein JL, Chen LY, et al. Trends in partial and radical nephrectomy: an analysis of case logs from certifying urologists. J Urol 2013; 190: 464–469. 14. Lane BR, Golan S, Eggener S, et al. Differential use of partial nephrectomy for intermediate and high complexity tumors may explain variability in & reported utilization rates. J Urol 2013; 189: 2047–2053. A study that shows that the underuse of partial nephrectomy in low-volume centers only concerns complex tumors. 15. Weight CJ, Crispen PL, Breau RH, et al. Practice-setting and surgeon characteristics heavily influence the decision to perform partial nephrectomy among American Urologic Association surgeons. BJU Int 2013; 111: 731–738. 16. Abouassaly R, Finelli A, Tomlinson GA, et al. Volume-outcome relationships in the treatment of renal tumors. J Urol 2012; 187: 1984–1988. 17. Patel HD, Mullins JK, Pierorazio PM, et al. Trends in renal surgery: robotic technology is associated with increased use of partial nephrectomy. J Urol & 2013; 189: 1229–1235. A study that suggests that robotic technology is associated with an increased use of partial nephrectomy regardless of surgical volume. 18. Abouassaly R, Alibhai SM, Tomlinson G, et al. Unintended consequences of laparoscopic surgery on partial nephrectomy for kidney cancer. J Urol 2010; 183: 467. 19. Gill IS, Kamoi K, Aron M, et al. 800 Laparoscopic partial nephrectomies: a single surgeon series. J Urol 2010; 183: 34–41. 20. Porpiglia F, Bertolo R, Amparore D, et al. Margins, ischaemia and complications rate after laparoscopic partial nephrectomy: impact of learning curve and tumour anatomical characteristics. BJU Int 2013; 112: 1125–1132. 21. Pierorazio PM, Patel HD, Feng T, et al. Robotic-assisted versus traditional laparoscopic partial nephrectomy: comparison of outcomes and evaluation of learning curve. Urology 2011; 78: 813–819. 22. Haseebuddin M, Benway BM, Cabello JM, et al. Robot-assisted partial nephrectomy: evaluation of learning curve for an experienced renal surgeon. J Endourol 2010; 24: 57–61. 23. Mottrie A, De Naeyer G, Schatteman P, et al. Impact of the learning curve on perioperative outcomes in patients who underwent robotic partial nephrectomy for parenchymal renal tumours. Eur Urol 2010; 58: 127– 132. &&
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