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Review Article

Ann Liver Transplant 2022; 2(1): 8-14

Published online May 31, 2022 https://doi.org/10.52604/alt.22.0011

Copyright © The Korean Liver Transplantation Society.

Association between institutional liver transplantation cases volume and mortality: A meta-analysis of Korea-nationwide cohort studies using Korean National Healthcare Insurance Service database

Yong-Kyu Chung1 , Cheon-Soo Park2 , Sung-Hwa Kang3

1Department of Surgery, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea
2Department of Surgery, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
3Department of Surgery, Dong-A University Hospital, College of Medicine, Dong-A University, Busan, Korea

Correspondence to:Yong-Kyu Chung
Department of Surgery, Haeundae Paik Hospital, Inje University College of Medicine, 875 Haeun-daero, Haeundae-gu, Busan 48108, Korea
E-mail: iteacher13@gmail.com
https://orcid.org/0000-0002-2132-2450

Received: March 28, 2022; Revised: April 1, 2022; Accepted: April 10, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Institutional case volume of liver transplantation (LT) is reported to be not associated with post-transplant survival in the United States, but their association was presented in several Korea-nationwide studies. Considering that the majority of LT centers in Korea are classified as low-volume centers, it is necessary to evaluate the effect of institutional LT case volume on post-transplant outcomes through a meta-analysis. This meta-analysis included four Korea-nationwide cohort studies using the database of Korean National Healthcare Insurance Service (NHIS) that focused on adult deceased donor liver transplantation (DDLT), adult living donor liver transplantation (LDLT), pediatric LT, and liver re-transplantation. A total of 1,616 LT cases were performed in 56 centers in the year 2020. DDLT and LDLT were performed in 46 and 51 centers, respectively. A total of 2,648 adult DDLTs were performed at 54 centers. Centers were divided into high (>30 LTs/year)-, medium (10–30)-, and low (<10)-volume centers; and their in-hospital mortality (IHM) rates were 10.3%, 14.3%, and 17.1%, respectively. A total of 7,073 adult LDLTs were performed at 50 centers. Centers were divided into high (>50)-, medium (10-50)-, and low (<10)-volume centers; and their IHM rates were 2.8%, 4.1%, and 6.7%, respectively. A total of 521 pediatric LTs were performed at 22 centers. Centers were divided into high (>10)-, medium (1–10)-, and low (<1)-volume centers; and their IHM rates were 5.8%, 12.5%, and 32.1%, respectively. A total of 258 liver re-transplantation were performed; 175 cases were performed in 3 high-volume (≥64) centers and 83 cases were performed in 21 low-volume (<64) centers; and their IHM rates were 25% and 36%, respectively. The results of the present meta-analysis revealed the lower IHM rates in high-volume LT centers compared with low-volume centers regarding all types of LT including DDLT, adult LDLT, pediatric LT, and liver re-transplantation.

Keywords: Deceased donor liver transplantation, Living donor liver transplantation, Pediatric liver transplantation, Liver retransplantation, Mortality

For many complex surgical procedures, there is an association between a low volume of procedures and an increased risk of death. Liver transplantation (LT) is regarded as one of the most complex surgical procedures, thus LT outcomes may be influenced by the LT team experience. In the United States (US), transplant centers performing ≤20 LT cases per year showed a higher mortality rate than the higher LT volume centers [1]. In contrast, it was reported that institutional case volume was not a significant predictor of post-transplant survival in the model for the end-stage liver disease (MELD) era [2]. In the US studies to examine whether individual surgeon volume is associated with LT outcomes, there was no significant relationship between LT volume and LT outcomes at the transplant center level [3,4]. These data suggest that the quality of LT teams performing deceased donor liver transplantation (DDLT) may be equalized in most of the US LT centers.

On the other hand, a cohort study using Korea-nationwide data revealed better in-hospital mortality (IHM) and long-term survival after DDLT in the high-volume LT centers compared to low-volume centers [5]. Another Korea-nationwide retrospective cohort study also revealed that high-volume LT centers also had better outcomes after living donor liver transplantation (LDLT) and pediatric LT compared with low-volume centers [6,7]. In 2020, 1,616 cases of LT, 46 DDLT, and 51 LDLT cases, were performed in 56 centers in Korea [8]. Considering that the majority of LT centers in Korea are classified as low-volume centers, it is necessary to evaluate the effect of institutional LT cases volume on post-transplant outcomes through a meta-analysis.

A total of 1,616 LT cases were performed in 56 centers in the year 2020. DDLT and LDLT were performed in 46 and 51 centers, respectively. Five centers performed DDLT only, and their LT volume was one or two cases. Ten centers performed LDLT only, with LT volume of one or two cases in eight centers, but 8 and 28 cases each were reported at two centers. Forty-one centers performed both DDLT and LDLT (Fig. 1) [8].

Figure 1.Distribution of Korean transplantation centers performing deceased donor liver transplantations (DDLT) and living donor liver transplantations (LDLT) in 2020. LT, liver transplantation.

In the year 2020, 31 (55.4%) centers performed 1 to 10 LTs; 13 (23.2%) centers reported 11 to 25 LTs; 7 (12.5%) centers performed 26 to 50 LTs; one (1.8%) center conducted 55 LTs; three centers had LT volume of 118, 139 and 151 each; and one (1.8%) center reported 511 LTs. The latter five major centers performed 974 LTs, which accounted for 60.3% of the LT volume nationwide in the year 2020. The 511 LTs performed at a single center constituted 31.6% of the nationwide LT volume. These major five LT centers performed 179 cases of DDLT, which accounted for 45.3% of the nationwide DDLT volume; and also performed 795 LDLTs, which constituted 65.1% of the nationwide LDLT volume (p<0.001). These findings suggest that LDLT was predominantly performed at these high-volume LT centers [8].

A nationwide retrospective cohort study was performed to investigate the relationship between institutional case volume and post-transplant outcomes after DDLT. The data was extracted from the Korean National Healthcare Insurance Service (NHIS) database. A total of 2,648 adult DDLTs were performed at 54 centers from January 2007 to December 2016. Centers were divided into high-, medium-, and low-volume centers according to the average annual number of DDLTs: <10, 10–30, and >30, respectively. The IHM rates in high-, medium-, and low-volume centers were 10.3%, 14.3%, and 17.1%, respectively (Fig. 2). Multivariable logistic regression analysis revealed that low-volume centers (adjusted relative risk [RR]=1.953; 95% confidence interval [CI]=1.461–2.611; p<0.001) and medium-volume centers (adjusted RR=1.480; 95% CI=1.098–1.994; p=0.010) had a significantly higher IHM rate compared to high-volume centers. Long-term mortality rates were also higher in low-volume centers (p=0.007) (Fig. 3). This study concluded that centers with higher volume showed better IHM and long-term survival after DDLT compared to centers with lower volume [5].

Figure 2.Relationship between the average annual number of deceased donor liver transplantation (DDLT) and in-hospital mortality at 54 centers, from 2007 to 2016. High-volume center: >30 liver transplantations (LTs)/year, Medium-volume center: 10–30 LTs/year, Low-volume center: <10 LTs/year.

Figure 3.Kaplan-Meier survival curve after adult deceased donor liver transplantation (DDLT) according to the center case volume.

A nationwide retrospective cohort study using the Korean NHIS database aimed to evaluate the relationship between institutional case volume and clinical outcomes after adult LDLT. Between January 2007 and December 2016, 7,073 adult LDLTs were performed at 50 centers in Korea. Centers were categorized as high-, medium-, and low-volume centers according to the average annual number of LTs: >50, 10 to 50, and <10, respectively. The IHM rates in the high-, medium-, and low-volume centers were 2.8%, 4.1%, and 6.7%, respectively (Fig. 4). After adjustment, the IHM rate was significantly higher in the low-volume centers (adjusted RR=2.287; 95% CI=1.471–3.557; p<0.001) and medium-volume centers (adjusted RR=1.676; 95% CI=1.089–2.578; p=0.019) compared with high-volume centers (Fig. 5). The high-volume centers showed that long-term survival for up to 9 years was better, and intensive care unit and hospital length of stay were shorter. This study concluded that centers with higher cases volume (>50 LTs/year) had better outcomes after adult LDLT, including IHM and long-term mortality compared with centers with lower case volumes (≤50 LTs/year) [6].

Figure 4.Relationship between the average annual volume and in-hospital mortality after adult living donor liver transplantation. High-volume center: >50 liver transplantations (LTs)/year, Medium-volume center: 10–50 LTs/year, Low-volume center: <10 LTs/year.

Figure 5.Kaplan-Meier survival curve after adult living donor liver transplantation according to the center case volume.

A nationwide retrospective cohort study using the Korean NHIS database was conducted to evaluate whether institutional cases volume affects clinical outcomes after pediatric LT. Between January 2007 and December 2016, 521 pediatric LTs were performed at 22 centers in Korea. Centers were categorized as high-, medium-, and low-volume centers according to the average annual number of LTs: >10, 1 to 10, and <1, respectively. The IHM rates in the high-, medium-, and low-volume centers were 5.8%, 12.5%, and 32.1%, respectively (Fig. 6). After adjustment, the IHM rate was significantly higher in the low-volume centers (adjusted RR=9.693; 95% CI=4.636–20.268; p<0.001) and medium-volume centers (adjusted RR=3.393; 95% CI=1.980–5.813; p<0.001) compared to high-volume centers. Long-term survival for up to 9 years was better in high-volume centers (Fig. 7). This study concluded that centers with higher cases volume (>10 pediatric LTs/year) had better outcomes after pediatric LT, including IHM and long-term mortality, compared to centers with lower case volumes (≤10 LTs/year) [7].

Figure 6.Average annual case volume and in-hospital mortality after pediatric liver transplantation (LT). High-volume center: >10 LTs/year, Medium-volume center: 1–10 LTs/year, Low-volume center: <1 LTs/year.

Figure 7.Kaplan-Meier survival curve after pediatric liver transplantation (LT) according to the center case volume.

The relationship between institutional LT case volume and clinical outcomes after liver re-transplantation was assessed through analysis of the patients who underwent liver re-transplantation between 2007 and 2016. They were selected from the Korean NHIS database. LT centers were categorized to either high-volume centers (≥64 LTs/year) or low-volume centers (<64 LTs/year) according to the annual LT case volume. A total of 258 liver re-transplantations were performed during the study period: 175 liver re-transplantations were performed in three high-volume centers and 83 were performed in 21 low-volume centers. The IHM rates after liver re-transplantation in high and low-volume centers were 25% and 36%, respectively (p=0.069; Fig. 8). Adjusted IHM rate was not different between low and high-volume centers. Adjusted 1-year mortality was significantly higher in low-volume centers (RR=2.14; 95% CI=1.05–4.37, p=0.037) compared to high-volume centers. Long-term survival for up to 9 years was also higher in the high-volume centers (p=0.005; Fig. 9). Other risk factors of IHM and 1-year mortality included female gender and higher Elixhauser comorbidity index. This study concluded that centers with higher case volume (≥64 LTs/year) showed lower IHM and overall mortality after liver re-transplantation compared to low-volume centers [9].

Figure 8.Relation between the institutional cases volume and in-hospital mortality after liver re-transplantation. High-volume center: ≥64 LTs/year, Low-volume center: <64 LTs/year. LT, liver transplantation.

Figure 9.Kaplan-Meier survival curve after liver re-transplantation according to the center case volume. LT, liver transplantation.

Long-term mortality rates of the above-mentioned four cohort studies for DDLT, adult LDLT, pediatric LT, and liver re-transplantation were analyzed [5-7,9]. Meta-analysis of these data showed that high-volume LT centers had lower mortality rates compared with low-volume centers (RR=0.710; 95% CI=0.533–0.911; Fig. 10).

Figure 10.Fig. 10 . Forest plot of four Korea-nationwide cohort studies on LT. DDLT, deceased donor liver transplantation; LDLT, living donor liver transplantation; LT, liver transplantation; RR, relative risk; CI, confidence interval.

Four Korea-nationwide cohort studies on DDLT, adult LDLT, pediatric LT, and liver re-transplantation using the Korean NHIS database revealed that high-volume LT center had lower mortality rates compared with low-volume centers [5-7,9]. These Korean studies disagree with those of the high-volume US cohort studies using the registry data from the Organ Procurement Transplantation Network [2-4].

The impact of institutional cases volume on post-transplant outcomes may differ depending on the complexity of the surgical procedure. The cases volume effect on postoperative clinical outcome have been reported in complex surgical procedures [10], while institutional case volume did not influence clinical outcomes in relatively simple surgical procedures [11]. Therefore, complex surgical procedures have are preferably performed in high-volume centers with regards to patient outcomes. The present study analysis results suggest that higher institutional case volume is associated with improved short- and long-term survival after LT.

The results of the present meta-analysis may be used as evidence supporting centralization of LT. Patients requiring complex and high-risk surgical procedures may anticipate better outcomes when they receive care in designated centers with sufficient experience. Our previous study revealed that the number of LT centers in Korea was 56 in the year 2020 [8]. Forty-one transplant centers performed both DDLT and LDLT, five centers performed only DDLT, and 10 centers conducted only LDLT. Five major centers performed 974 cases, which accounted for 60.3% of nationwide LT volume in 2020. These centers performed 45.3% of all the nationwide DDLT volume and 65.1% of the nationwide LDLT volume in 2020, indicating that LDLT was highly concentrated at these high-volume LT centers [8].

There is no clear cutoff between the high and low-volume centers based on patient outcome after LT. Considering that the LDLT surgical techniques have been gradually standardized in Korea and those of DDLT are well established already worldwide [12-15], it is expected that with the accumulation of institutional experience in small-volume LT centers, the difference in post-transplant outcomes in the near past data would be diluted in the near future. The old cohort studies in the US indicated the presence of inter-center differences [1], but similar studies after the year 2000 have reported the absence of such differences, especially after the adoption of the MELD score system [2,3]. Liver re-transplantation is a demanding procedure, much more difficult than primary LT. A US cohort study revealed that center volume is an imprecise surrogate measure for 1-year outcomes after liver re-transplantation [4].

The completeness of the NIHS database in coverage of the whole Korean population is a unique strength of the four cohort studies included in the present meta-analysis. The Korea healthcare system is a single-payer system and insures more than 97% of residents in Korea [12] with equal benefits, regardless of the insurance premiums that differ depending on income. The remaining 3% of the population with the lowest income is supported by the Medical Aid program. The bulk of the incurred medical expenses are reimbursed by the NHIS and the details of the claim is stored in the NHIS database. Therefore, the four cohort studies are free from selection bias, or incomplete/missing data regarding the outcomes. Due to the completeness of the Korean NHIS database, the results of the present study may reflect the real-world outcomes after LT.

In conclusion, the results of the present meta-analysis revealed lower mortality rates in high-volume LT centers compared with low-volume centers regarding all type of LT, including DDLT, adult LDLT, pediatric LT, and liver re-transplantation. Considering that the surgical techniques for LDLT have been gradually standardized and those for DDLT are established already, it is expected that with the accumulation of institutional experience in small-volume LT centers, the difference in post-transplant outcomes experienced in the near past data would be compensated in the near future.

  1. Edwards EB, Roberts JP, McBride MA, Schulak JA, Hunsicker LG. The effect of the volume of procedures at transplantation centers on mortality after liver transplantation. N Engl J Med 1999;341:2049-2053.
    Pubmed CrossRef
  2. Northup PG, Pruett TL, Stukenborg GJ, Berg CL. Survival after adult liver transplantation does not correlate with transplant center case volume in the MELD era. Am J Transplant 2006;6:2455-2462.
    Pubmed CrossRef
  3. Scarborough JE, Pietrobon R, Tuttle-Newhall JE, Marroquin CE, Collins BH, Desai DM, et al. Relationship between provider volume and outcomes for orthotopic liver transplantation. J Gastrointest Surg 2008;12:1527-1533.
    Pubmed CrossRef
  4. Reese PP, Yeh H, Thomasson AM, Shults J, Markmann JF. Transplant center volume and outcomes after liver retransplantation. Am J Transplant 2009;9:309-317.
    Pubmed KoreaMed CrossRef
  5. Yoo S, Jang EJ, Kim GH, Kim DH, Kwon SM, Lee H, et al. Effect of institutional case volume on in-hospital mortality after deceased donor liver transplantation: a nationwide retrospective cohort study in Korea. Transplant Proc 2018;50:3644-3649.
    Pubmed CrossRef
  6. Yoo S, Jang EJ, Yi NJ, Kim GH, Kim DH, Lee H, et al. Effect of institutional case volume on in-hospital mortality after living donor liver transplantation: analysis of 7073 cases between 2007 and 2016 in Korea. Transplantation 2019;103:952-958.
    Pubmed CrossRef
  7. Lee H, Jang EJ, Kim GH, Yi NJ, Kim DH, Yoo S, et al. Effect of case volume on mortality after pediatric liver transplantation in Korea. Transplantation 2019;103:1649-1654.
    Pubmed CrossRef
  8. Chung YK, Kang SH. Analysis of nationwide volume of liver transplantation in Korea during 2020 shows no definitive decrease during COVID-19 outbreak. Ann Liver Transplant 2021;1:135-139.
    CrossRef
  9. Oh SY, Jang EJ, Kim GH, Lee H, Yi NJ, Yoo S, et al. Association between hospital liver transplantation volume and mortality after liver re-transplantation. PLoS One 2021;16:e0255655.
    Pubmed KoreaMed CrossRef
  10. Hata T, Motoi F, Ishida M, Naitoh T, Katayose Y, Egawa S, et al. Effect of hospital volume on surgical outcomes after pancreaticoduodenectomy: a systematic review and meta-analysis. Ann Surg 2016;263:664-672.
    Pubmed CrossRef
  11. Murphy MM, Ng SC, Simons JP, Csikesz NG, Shah SA, Tseng JF. Predictors of major complications after laparoscopic cholecystectomy: surgeon, hospital, or patient? J Am Coll Surg 2010;211:73-80.
    Pubmed CrossRef
  12. Hwang S, Lee SG, Ahn CS, Moon DB, Kim KH, Sung KB, et al. Morphometric and simulation analyses of right hepatic vein reconstruction in adult living donor liver transplantation using right lobe grafts. Liver Transpl 2010;16:639-648.
    Pubmed CrossRef
  13. Hwang S, Ahn CS, Kim KH, Moon DB, Ha TY, Song GW, et al. Standardization of modified right lobe grafts to minimize vascular outflow complications for adult living donor liver transplantation. Transplant Proc 2012;44:457-459.
    Pubmed CrossRef
  14. Hwang S, Ha TY, Ahn CS, Moon DB, Kim KH, Song GW, et al. Standardized surgical techniques for adult living donor liver transplantation using a modified right lobe graft: a video presentation from bench to reperfusion. Korean J Hepatobiliary Pancreat Surg 2016;20:97-101.
    Pubmed KoreaMed CrossRef
  15. Koo BK, Lee CH, Yang BR, Hwang SS, Choi NK. The incidence and prevalence of diabetes mellitus and related atherosclerotic complications in Korea: a National Health Insurance database study. PLoS One 2014;9:e110650.
    Pubmed KoreaMed CrossRef

Article

Review Article

Ann Liver Transplant 2022; 2(1): 8-14

Published online May 31, 2022 https://doi.org/10.52604/alt.22.0011

Copyright © The Korean Liver Transplantation Society.

Association between institutional liver transplantation cases volume and mortality: A meta-analysis of Korea-nationwide cohort studies using Korean National Healthcare Insurance Service database

Yong-Kyu Chung1 , Cheon-Soo Park2 , Sung-Hwa Kang3

1Department of Surgery, Haeundae Paik Hospital, Inje University College of Medicine, Busan, Korea
2Department of Surgery, Eunpyeong St. Mary’s Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea
3Department of Surgery, Dong-A University Hospital, College of Medicine, Dong-A University, Busan, Korea

Correspondence to:Yong-Kyu Chung
Department of Surgery, Haeundae Paik Hospital, Inje University College of Medicine, 875 Haeun-daero, Haeundae-gu, Busan 48108, Korea
E-mail: iteacher13@gmail.com
https://orcid.org/0000-0002-2132-2450

Received: March 28, 2022; Revised: April 1, 2022; Accepted: April 10, 2022

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Institutional case volume of liver transplantation (LT) is reported to be not associated with post-transplant survival in the United States, but their association was presented in several Korea-nationwide studies. Considering that the majority of LT centers in Korea are classified as low-volume centers, it is necessary to evaluate the effect of institutional LT case volume on post-transplant outcomes through a meta-analysis. This meta-analysis included four Korea-nationwide cohort studies using the database of Korean National Healthcare Insurance Service (NHIS) that focused on adult deceased donor liver transplantation (DDLT), adult living donor liver transplantation (LDLT), pediatric LT, and liver re-transplantation. A total of 1,616 LT cases were performed in 56 centers in the year 2020. DDLT and LDLT were performed in 46 and 51 centers, respectively. A total of 2,648 adult DDLTs were performed at 54 centers. Centers were divided into high (>30 LTs/year)-, medium (10–30)-, and low (<10)-volume centers; and their in-hospital mortality (IHM) rates were 10.3%, 14.3%, and 17.1%, respectively. A total of 7,073 adult LDLTs were performed at 50 centers. Centers were divided into high (>50)-, medium (10-50)-, and low (<10)-volume centers; and their IHM rates were 2.8%, 4.1%, and 6.7%, respectively. A total of 521 pediatric LTs were performed at 22 centers. Centers were divided into high (>10)-, medium (1–10)-, and low (<1)-volume centers; and their IHM rates were 5.8%, 12.5%, and 32.1%, respectively. A total of 258 liver re-transplantation were performed; 175 cases were performed in 3 high-volume (≥64) centers and 83 cases were performed in 21 low-volume (<64) centers; and their IHM rates were 25% and 36%, respectively. The results of the present meta-analysis revealed the lower IHM rates in high-volume LT centers compared with low-volume centers regarding all types of LT including DDLT, adult LDLT, pediatric LT, and liver re-transplantation.

Keywords: Deceased donor liver transplantation, Living donor liver transplantation, Pediatric liver transplantation, Liver retransplantation, Mortality

INTRODUCTION

For many complex surgical procedures, there is an association between a low volume of procedures and an increased risk of death. Liver transplantation (LT) is regarded as one of the most complex surgical procedures, thus LT outcomes may be influenced by the LT team experience. In the United States (US), transplant centers performing ≤20 LT cases per year showed a higher mortality rate than the higher LT volume centers [1]. In contrast, it was reported that institutional case volume was not a significant predictor of post-transplant survival in the model for the end-stage liver disease (MELD) era [2]. In the US studies to examine whether individual surgeon volume is associated with LT outcomes, there was no significant relationship between LT volume and LT outcomes at the transplant center level [3,4]. These data suggest that the quality of LT teams performing deceased donor liver transplantation (DDLT) may be equalized in most of the US LT centers.

On the other hand, a cohort study using Korea-nationwide data revealed better in-hospital mortality (IHM) and long-term survival after DDLT in the high-volume LT centers compared to low-volume centers [5]. Another Korea-nationwide retrospective cohort study also revealed that high-volume LT centers also had better outcomes after living donor liver transplantation (LDLT) and pediatric LT compared with low-volume centers [6,7]. In 2020, 1,616 cases of LT, 46 DDLT, and 51 LDLT cases, were performed in 56 centers in Korea [8]. Considering that the majority of LT centers in Korea are classified as low-volume centers, it is necessary to evaluate the effect of institutional LT cases volume on post-transplant outcomes through a meta-analysis.

DISTRIBUTION OF LIVER TRANSPLANTATION CASES PER TRANSPLANT CENTER IN KOREA DURING THE YEAR 2020

A total of 1,616 LT cases were performed in 56 centers in the year 2020. DDLT and LDLT were performed in 46 and 51 centers, respectively. Five centers performed DDLT only, and their LT volume was one or two cases. Ten centers performed LDLT only, with LT volume of one or two cases in eight centers, but 8 and 28 cases each were reported at two centers. Forty-one centers performed both DDLT and LDLT (Fig. 1) [8].

Figure 1. Distribution of Korean transplantation centers performing deceased donor liver transplantations (DDLT) and living donor liver transplantations (LDLT) in 2020. LT, liver transplantation.

In the year 2020, 31 (55.4%) centers performed 1 to 10 LTs; 13 (23.2%) centers reported 11 to 25 LTs; 7 (12.5%) centers performed 26 to 50 LTs; one (1.8%) center conducted 55 LTs; three centers had LT volume of 118, 139 and 151 each; and one (1.8%) center reported 511 LTs. The latter five major centers performed 974 LTs, which accounted for 60.3% of the LT volume nationwide in the year 2020. The 511 LTs performed at a single center constituted 31.6% of the nationwide LT volume. These major five LT centers performed 179 cases of DDLT, which accounted for 45.3% of the nationwide DDLT volume; and also performed 795 LDLTs, which constituted 65.1% of the nationwide LDLT volume (p<0.001). These findings suggest that LDLT was predominantly performed at these high-volume LT centers [8].

ASSOCIATION BETWEEN INSTITUTIONAL ADULT DECEASED DONOR LIVER TRANSPLANTATION VOLUME AND POST-TRANSPLANT OUTCOMES IN KOREA

A nationwide retrospective cohort study was performed to investigate the relationship between institutional case volume and post-transplant outcomes after DDLT. The data was extracted from the Korean National Healthcare Insurance Service (NHIS) database. A total of 2,648 adult DDLTs were performed at 54 centers from January 2007 to December 2016. Centers were divided into high-, medium-, and low-volume centers according to the average annual number of DDLTs: <10, 10–30, and >30, respectively. The IHM rates in high-, medium-, and low-volume centers were 10.3%, 14.3%, and 17.1%, respectively (Fig. 2). Multivariable logistic regression analysis revealed that low-volume centers (adjusted relative risk [RR]=1.953; 95% confidence interval [CI]=1.461–2.611; p<0.001) and medium-volume centers (adjusted RR=1.480; 95% CI=1.098–1.994; p=0.010) had a significantly higher IHM rate compared to high-volume centers. Long-term mortality rates were also higher in low-volume centers (p=0.007) (Fig. 3). This study concluded that centers with higher volume showed better IHM and long-term survival after DDLT compared to centers with lower volume [5].

Figure 2. Relationship between the average annual number of deceased donor liver transplantation (DDLT) and in-hospital mortality at 54 centers, from 2007 to 2016. High-volume center: >30 liver transplantations (LTs)/year, Medium-volume center: 10–30 LTs/year, Low-volume center: <10 LTs/year.

Figure 3. Kaplan-Meier survival curve after adult deceased donor liver transplantation (DDLT) according to the center case volume.

ASSOCIATION BETWEEN INSTITUTIONAL ADULT LIVING DONOR LIVER TRANSPLANTATION VOLUME AND POST-TRANSPLANT OUTCOMES IN KOREA

A nationwide retrospective cohort study using the Korean NHIS database aimed to evaluate the relationship between institutional case volume and clinical outcomes after adult LDLT. Between January 2007 and December 2016, 7,073 adult LDLTs were performed at 50 centers in Korea. Centers were categorized as high-, medium-, and low-volume centers according to the average annual number of LTs: >50, 10 to 50, and <10, respectively. The IHM rates in the high-, medium-, and low-volume centers were 2.8%, 4.1%, and 6.7%, respectively (Fig. 4). After adjustment, the IHM rate was significantly higher in the low-volume centers (adjusted RR=2.287; 95% CI=1.471–3.557; p<0.001) and medium-volume centers (adjusted RR=1.676; 95% CI=1.089–2.578; p=0.019) compared with high-volume centers (Fig. 5). The high-volume centers showed that long-term survival for up to 9 years was better, and intensive care unit and hospital length of stay were shorter. This study concluded that centers with higher cases volume (>50 LTs/year) had better outcomes after adult LDLT, including IHM and long-term mortality compared with centers with lower case volumes (≤50 LTs/year) [6].

Figure 4. Relationship between the average annual volume and in-hospital mortality after adult living donor liver transplantation. High-volume center: >50 liver transplantations (LTs)/year, Medium-volume center: 10–50 LTs/year, Low-volume center: <10 LTs/year.

Figure 5. Kaplan-Meier survival curve after adult living donor liver transplantation according to the center case volume.

ASSOCIATION BETWEEN INSTITUTIONAL PEDIATRIC LIVER TRANSPLANTATION VOLUME AND POST-TRANSPLANT OUTCOMES IN KOREA

A nationwide retrospective cohort study using the Korean NHIS database was conducted to evaluate whether institutional cases volume affects clinical outcomes after pediatric LT. Between January 2007 and December 2016, 521 pediatric LTs were performed at 22 centers in Korea. Centers were categorized as high-, medium-, and low-volume centers according to the average annual number of LTs: >10, 1 to 10, and <1, respectively. The IHM rates in the high-, medium-, and low-volume centers were 5.8%, 12.5%, and 32.1%, respectively (Fig. 6). After adjustment, the IHM rate was significantly higher in the low-volume centers (adjusted RR=9.693; 95% CI=4.636–20.268; p<0.001) and medium-volume centers (adjusted RR=3.393; 95% CI=1.980–5.813; p<0.001) compared to high-volume centers. Long-term survival for up to 9 years was better in high-volume centers (Fig. 7). This study concluded that centers with higher cases volume (>10 pediatric LTs/year) had better outcomes after pediatric LT, including IHM and long-term mortality, compared to centers with lower case volumes (≤10 LTs/year) [7].

Figure 6. Average annual case volume and in-hospital mortality after pediatric liver transplantation (LT). High-volume center: >10 LTs/year, Medium-volume center: 1–10 LTs/year, Low-volume center: <1 LTs/year.

Figure 7. Kaplan-Meier survival curve after pediatric liver transplantation (LT) according to the center case volume.

ASSOCIATION BETWEEN INSTITUTIONAL LIVER TRANSPLANTATION VOLUME AND OUTCOMES OF LIVER RE-TRANSPLANTATION IN KOREA

The relationship between institutional LT case volume and clinical outcomes after liver re-transplantation was assessed through analysis of the patients who underwent liver re-transplantation between 2007 and 2016. They were selected from the Korean NHIS database. LT centers were categorized to either high-volume centers (≥64 LTs/year) or low-volume centers (<64 LTs/year) according to the annual LT case volume. A total of 258 liver re-transplantations were performed during the study period: 175 liver re-transplantations were performed in three high-volume centers and 83 were performed in 21 low-volume centers. The IHM rates after liver re-transplantation in high and low-volume centers were 25% and 36%, respectively (p=0.069; Fig. 8). Adjusted IHM rate was not different between low and high-volume centers. Adjusted 1-year mortality was significantly higher in low-volume centers (RR=2.14; 95% CI=1.05–4.37, p=0.037) compared to high-volume centers. Long-term survival for up to 9 years was also higher in the high-volume centers (p=0.005; Fig. 9). Other risk factors of IHM and 1-year mortality included female gender and higher Elixhauser comorbidity index. This study concluded that centers with higher case volume (≥64 LTs/year) showed lower IHM and overall mortality after liver re-transplantation compared to low-volume centers [9].

Figure 8. Relation between the institutional cases volume and in-hospital mortality after liver re-transplantation. High-volume center: ≥64 LTs/year, Low-volume center: <64 LTs/year. LT, liver transplantation.

Figure 9. Kaplan-Meier survival curve after liver re-transplantation according to the center case volume. LT, liver transplantation.

META-ANALYSIS OF RELATIVE RISK FOR POST-TRANSPLANT MORTALITY

Long-term mortality rates of the above-mentioned four cohort studies for DDLT, adult LDLT, pediatric LT, and liver re-transplantation were analyzed [5-7,9]. Meta-analysis of these data showed that high-volume LT centers had lower mortality rates compared with low-volume centers (RR=0.710; 95% CI=0.533–0.911; Fig. 10).

Figure 10. Fig. 10 . Forest plot of four Korea-nationwide cohort studies on LT. DDLT, deceased donor liver transplantation; LDLT, living donor liver transplantation; LT, liver transplantation; RR, relative risk; CI, confidence interval.

DISCUSSION

Four Korea-nationwide cohort studies on DDLT, adult LDLT, pediatric LT, and liver re-transplantation using the Korean NHIS database revealed that high-volume LT center had lower mortality rates compared with low-volume centers [5-7,9]. These Korean studies disagree with those of the high-volume US cohort studies using the registry data from the Organ Procurement Transplantation Network [2-4].

The impact of institutional cases volume on post-transplant outcomes may differ depending on the complexity of the surgical procedure. The cases volume effect on postoperative clinical outcome have been reported in complex surgical procedures [10], while institutional case volume did not influence clinical outcomes in relatively simple surgical procedures [11]. Therefore, complex surgical procedures have are preferably performed in high-volume centers with regards to patient outcomes. The present study analysis results suggest that higher institutional case volume is associated with improved short- and long-term survival after LT.

The results of the present meta-analysis may be used as evidence supporting centralization of LT. Patients requiring complex and high-risk surgical procedures may anticipate better outcomes when they receive care in designated centers with sufficient experience. Our previous study revealed that the number of LT centers in Korea was 56 in the year 2020 [8]. Forty-one transplant centers performed both DDLT and LDLT, five centers performed only DDLT, and 10 centers conducted only LDLT. Five major centers performed 974 cases, which accounted for 60.3% of nationwide LT volume in 2020. These centers performed 45.3% of all the nationwide DDLT volume and 65.1% of the nationwide LDLT volume in 2020, indicating that LDLT was highly concentrated at these high-volume LT centers [8].

There is no clear cutoff between the high and low-volume centers based on patient outcome after LT. Considering that the LDLT surgical techniques have been gradually standardized in Korea and those of DDLT are well established already worldwide [12-15], it is expected that with the accumulation of institutional experience in small-volume LT centers, the difference in post-transplant outcomes in the near past data would be diluted in the near future. The old cohort studies in the US indicated the presence of inter-center differences [1], but similar studies after the year 2000 have reported the absence of such differences, especially after the adoption of the MELD score system [2,3]. Liver re-transplantation is a demanding procedure, much more difficult than primary LT. A US cohort study revealed that center volume is an imprecise surrogate measure for 1-year outcomes after liver re-transplantation [4].

The completeness of the NIHS database in coverage of the whole Korean population is a unique strength of the four cohort studies included in the present meta-analysis. The Korea healthcare system is a single-payer system and insures more than 97% of residents in Korea [12] with equal benefits, regardless of the insurance premiums that differ depending on income. The remaining 3% of the population with the lowest income is supported by the Medical Aid program. The bulk of the incurred medical expenses are reimbursed by the NHIS and the details of the claim is stored in the NHIS database. Therefore, the four cohort studies are free from selection bias, or incomplete/missing data regarding the outcomes. Due to the completeness of the Korean NHIS database, the results of the present study may reflect the real-world outcomes after LT.

In conclusion, the results of the present meta-analysis revealed lower mortality rates in high-volume LT centers compared with low-volume centers regarding all type of LT, including DDLT, adult LDLT, pediatric LT, and liver re-transplantation. Considering that the surgical techniques for LDLT have been gradually standardized and those for DDLT are established already, it is expected that with the accumulation of institutional experience in small-volume LT centers, the difference in post-transplant outcomes experienced in the near past data would be compensated in the near future.

FUNDING

There was no funding related to this study.

CONFLICT OF INTEREST

All authors have no conflicts of interest to declare.

AUTHORS’ CONTRIBUTIONS

Conceptualization: YKC. Data curation: All. Methodology: All. Visualization: All. Writing - original draft: All. Writing - review & editing: All.

Fig 1.

Figure 1.Distribution of Korean transplantation centers performing deceased donor liver transplantations (DDLT) and living donor liver transplantations (LDLT) in 2020. LT, liver transplantation.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 2.

Figure 2.Relationship between the average annual number of deceased donor liver transplantation (DDLT) and in-hospital mortality at 54 centers, from 2007 to 2016. High-volume center: >30 liver transplantations (LTs)/year, Medium-volume center: 10–30 LTs/year, Low-volume center: <10 LTs/year.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 3.

Figure 3.Kaplan-Meier survival curve after adult deceased donor liver transplantation (DDLT) according to the center case volume.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 4.

Figure 4.Relationship between the average annual volume and in-hospital mortality after adult living donor liver transplantation. High-volume center: >50 liver transplantations (LTs)/year, Medium-volume center: 10–50 LTs/year, Low-volume center: <10 LTs/year.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 5.

Figure 5.Kaplan-Meier survival curve after adult living donor liver transplantation according to the center case volume.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 6.

Figure 6.Average annual case volume and in-hospital mortality after pediatric liver transplantation (LT). High-volume center: >10 LTs/year, Medium-volume center: 1–10 LTs/year, Low-volume center: <1 LTs/year.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 7.

Figure 7.Kaplan-Meier survival curve after pediatric liver transplantation (LT) according to the center case volume.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 8.

Figure 8.Relation between the institutional cases volume and in-hospital mortality after liver re-transplantation. High-volume center: ≥64 LTs/year, Low-volume center: <64 LTs/year. LT, liver transplantation.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 9.

Figure 9.Kaplan-Meier survival curve after liver re-transplantation according to the center case volume. LT, liver transplantation.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

Fig 10.

Figure 10.Fig. 10 . Forest plot of four Korea-nationwide cohort studies on LT. DDLT, deceased donor liver transplantation; LDLT, living donor liver transplantation; LT, liver transplantation; RR, relative risk; CI, confidence interval.
Annals of Liver Transplantation 2022; 2: 8-14https://doi.org/10.52604/alt.22.0011

References

  1. Edwards EB, Roberts JP, McBride MA, Schulak JA, Hunsicker LG. The effect of the volume of procedures at transplantation centers on mortality after liver transplantation. N Engl J Med 1999;341:2049-2053.
    Pubmed CrossRef
  2. Northup PG, Pruett TL, Stukenborg GJ, Berg CL. Survival after adult liver transplantation does not correlate with transplant center case volume in the MELD era. Am J Transplant 2006;6:2455-2462.
    Pubmed CrossRef
  3. Scarborough JE, Pietrobon R, Tuttle-Newhall JE, Marroquin CE, Collins BH, Desai DM, et al. Relationship between provider volume and outcomes for orthotopic liver transplantation. J Gastrointest Surg 2008;12:1527-1533.
    Pubmed CrossRef
  4. Reese PP, Yeh H, Thomasson AM, Shults J, Markmann JF. Transplant center volume and outcomes after liver retransplantation. Am J Transplant 2009;9:309-317.
    Pubmed KoreaMed CrossRef
  5. Yoo S, Jang EJ, Kim GH, Kim DH, Kwon SM, Lee H, et al. Effect of institutional case volume on in-hospital mortality after deceased donor liver transplantation: a nationwide retrospective cohort study in Korea. Transplant Proc 2018;50:3644-3649.
    Pubmed CrossRef
  6. Yoo S, Jang EJ, Yi NJ, Kim GH, Kim DH, Lee H, et al. Effect of institutional case volume on in-hospital mortality after living donor liver transplantation: analysis of 7073 cases between 2007 and 2016 in Korea. Transplantation 2019;103:952-958.
    Pubmed CrossRef
  7. Lee H, Jang EJ, Kim GH, Yi NJ, Kim DH, Yoo S, et al. Effect of case volume on mortality after pediatric liver transplantation in Korea. Transplantation 2019;103:1649-1654.
    Pubmed CrossRef
  8. Chung YK, Kang SH. Analysis of nationwide volume of liver transplantation in Korea during 2020 shows no definitive decrease during COVID-19 outbreak. Ann Liver Transplant 2021;1:135-139.
    CrossRef
  9. Oh SY, Jang EJ, Kim GH, Lee H, Yi NJ, Yoo S, et al. Association between hospital liver transplantation volume and mortality after liver re-transplantation. PLoS One 2021;16:e0255655.
    Pubmed KoreaMed CrossRef
  10. Hata T, Motoi F, Ishida M, Naitoh T, Katayose Y, Egawa S, et al. Effect of hospital volume on surgical outcomes after pancreaticoduodenectomy: a systematic review and meta-analysis. Ann Surg 2016;263:664-672.
    Pubmed CrossRef
  11. Murphy MM, Ng SC, Simons JP, Csikesz NG, Shah SA, Tseng JF. Predictors of major complications after laparoscopic cholecystectomy: surgeon, hospital, or patient? J Am Coll Surg 2010;211:73-80.
    Pubmed CrossRef
  12. Hwang S, Lee SG, Ahn CS, Moon DB, Kim KH, Sung KB, et al. Morphometric and simulation analyses of right hepatic vein reconstruction in adult living donor liver transplantation using right lobe grafts. Liver Transpl 2010;16:639-648.
    Pubmed CrossRef
  13. Hwang S, Ahn CS, Kim KH, Moon DB, Ha TY, Song GW, et al. Standardization of modified right lobe grafts to minimize vascular outflow complications for adult living donor liver transplantation. Transplant Proc 2012;44:457-459.
    Pubmed CrossRef
  14. Hwang S, Ha TY, Ahn CS, Moon DB, Kim KH, Song GW, et al. Standardized surgical techniques for adult living donor liver transplantation using a modified right lobe graft: a video presentation from bench to reperfusion. Korean J Hepatobiliary Pancreat Surg 2016;20:97-101.
    Pubmed KoreaMed CrossRef
  15. Koo BK, Lee CH, Yang BR, Hwang SS, Choi NK. The incidence and prevalence of diabetes mellitus and related atherosclerotic complications in Korea: a National Health Insurance database study. PLoS One 2014;9:e110650.
    Pubmed KoreaMed CrossRef
The Korean Liver Transplantation Society

Vol.2 No.1
May, 2022

pISSN 2765-5121
eISSN 2765-6098

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