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Keywords:

  • Cardiovascular disease;
  • deceased donor;
  • living donor transplantation;
  • postoperative mortality;
  • survival

Abstract

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

To inform decision making regarding transplantation in patients ≥ 65 years, we quantified the early posttransplant risk of death by determining the time to equal risk and equal survival between transplant recipients and wait-listed dialysis patients in the United States between 1995 and 2007 (total n = 25 468). Survival was determined using separate multivariate nonproportional hazards analyses in low-, intermediate- and high-risk cardiovascular risk patients. Compared to wait-listed patients with similar cardiovascular risk, standard criteria (SCD) and expanded criteria (ECD) recipients had a higher risk of death in the perioperative and early-posttransplant period. In contrast, low and intermediate risk living donor (LD) recipients had an immediate survival advantage compared to similar risk wait-listed patients. In all risk groups, transplantation was associated with a long-term survival advantage compared to dialysis, but there were marked differences in time to equal risk of death, and time to equal survival by donor type. For example, survival in high-risk recipients of an LD, SCD and ECD transplant became equal to that in similar risk wait-listed patients 130, 368 and 521 days after transplantation. Early posttransplant mortality risk is eliminated in low- and intermediate-risk patients, and markedly reduced in high-risk patients with LD transplantation.


Abbreviations
DGF

delayed graft function

ECD

expanded criteria deceased donor

ESRD

end-stage renal disease

LD

living donor

SCD

standard criteria deceased donor

USRDS

United States Renal Data System.

Introduction

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

Kidney transplantation is the preferred treatment for patients with end-stage renal disease (ESRD), because it is associated with increased long-term survival and improved quality of life compared to treatment with dialysis [1, 2]. The benefits of transplantation are present in both young and old patients [3]. However, the survival advantage of deceased donor kidney transplantation is not recognized for approximately 8 months after the transplant surgery because of increased mortality during the perioperative and early posttransplant period, that is primarily due to cardiovascular disease [1]. The early mortality risk is likely higher in elderly patients because of age and a higher burden of comorbid disease, but also because elderly patients frequently undergo transplantation with older deceased donor kidneys that have a higher perioperative complication rate.

The physiological stress of transplant surgery is likely greater with a deceased compared to living donor. Deceased donor transplantation is uniquely an elective procedure involving patients at risk for cardiovascular disease performed under emergent conditions. Wait-listed patients summoned for urgent transplantation may not be medically optimized for surgery and a variety of unpredictable issues with the deceased donor kidney may complicate the transplant operation. In contrast, living donor transplantation provides an opportunity to optimize recipient medical management. Surgical considerations including the presence of recipient vascular disease and variation in donor anatomy are identified in advance of surgery and slow or delayed graft function is far less common than in deceased donor transplantation. To inform decision making regarding the use of different types of donors in the elderly, we quantified the early posttransplant risk of mortality by determining (1) the time to equal risk of death and (2) the time to equal survival between transplant recipients ≥ 65 years of a standard criteria deceased donor (SCD), expanded criteria deceased donor (ECD), or living donor (LD) and wait-listed dialysis patients of similar age and cardiovascular risk.

Methods

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

Study population and data source

All ESRD patients ≥ 65 years captured in the USRDS who initiated their first ESRD treatment (dialysis or preemptive transplantation) between April 1, 1995 and December 31, 2007 and were activated onto the deceased donor waiting list were included in the study. Patients were classified as low, intermediate or high cardiovascular risk if they had zero, one, or two of more of the following comorbid disease conditions: ischemic heart disease, congestive heart failure, cerebrovascular accident, peripheral vascular disease. In addition, all patients with diabetes as either the cause of ESRD or as a comorbid condition were considered high risk.

Definitions

Expanded criteria donor (ECD) was defined as all donors older than 60 years and donors older than 50 years with any two of the following criteria: (1) hypertension, (2) cerebrovascular cause of brain death, or (3) prerecovery of organs serum creatinine (SCr) level > 1.5 mg/dL.

Standard criteria donor (SCD) was defined when a deceased did not meet any of the criteria for ECD.

Delayed graft function (DGF) was defined by the requirement for dialysis in the first week after transplantation.

Analytical methods

Patient characteristics were described using proportions or mean (standard deviation) and group differences were compared with the chi-square for categorical variables or t-test for continuous variables.

Survival was determined from the date of activation to the waiting list with patients censored at time of permanent removal from the waiting list (for any reason), or December 31, 2007 using separate multivariate nonproportional hazards analyses in the low, intermediate and high cardiovascular risk groups with transplantation treated as a time-dependent covariate to account for the fact that patients switched treatment from dialysis to transplantation at different times. All analyses were intention to treat and patients were not censored at the time of allograft failure. The hazard for mortality in recipients of SCD, transplants compared to patients of similar risk who remained on the waiting list was determined by censoring follow-up at the time of transplantation from an ECD or living donor. These analyses were repeated with censoring at time of SCD and LD transplantation to determine the hazard for mortality in ECD recipients, and by censoring at time of SCD or ECD transplantation to determine the hazard for mortality in LD recipients. In each of these analyses the time to equal risk for mortality in transplant recipients compared to wait-list recipients of similar cardiovascular risk, as well as the time to equal survival, was determined. The multivariate models included adjustment for recipient, age, gender, race, cause of ESRD and year of wait listing. Similar analyses were performed to determine the time to equal risk for mortality, and time to equal survival in deceased donor recipients grouped by tertile of the donor only, kidney donor risk index (KDRI) [4]. The KDRI is a relative risk of posttransplant kidney allograft failure compared to that with a median (50th percentile) deceased donor.

Results

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

The characteristics of n = 25 468 study patients, including n = 11 425 (45%) low, n = 3 038 (12%) intermediate and n = 11 005 (43%) high cardiovascular risk patients are shown in Table 1. During the median follow-up of 2.67 (1.30, 4.78) years, n = 11 072 (43%) received a transplant including n = 5 825 (51%) of the low risk patients; n = 1 397 (46%) of the intermediate risk patients and n = 3 850 (35%) of the high-risk patients. During follow-up there were n = 6540 (25%) deaths on waiting list including n = 2289 (20%) of the low risk patients; n = 850 (28%) of the intermediate risk patients and n = 3401 (31%) of the high-risk patients. The risk of death was higher in patients with delayed graft function (DGF). The death rate in low-, intermediate-, and high-risk patients with DGF was 17, 15, 23 per 100 patient years compared to 4, 8, 10 per 100 patient years among those in the same risk groups without DGF. A total of n = 1489 patients (6%) were removed from waiting list including n = 633 (6%) of the low-risk patients; n = 185 (6%) of the intermediate risk patients and n = 671 (6%) of the high-risk patients. Among the 11 072 transplant recipients n = 3 600 (33%) died after transplantation, including n = 1 548 (27%) low risk, n = 468 (34%) intermediate risk, n = 1 584 (41%) high-risk patients). The use of SCD, ECD and LD transplantation was similar in low, intermediate and high-risk patients (Table 2). Preemptive transplantation was more frequent in low-risk patients, and median waiting times among nonpreemptive recipients were 1.0–1.2 years (Table 2).

Table 1. Patient characteristics (N = 25 468)
 Low riskIntermediateHigh risk 
 N =N =N = 
 11 425303811 005p-Value
  1. Patients were grouped as low, intermediate or high risk if they had 0, 1, ≥ 2 comorbid conditions. In addition patients with diabetes (recorded as either a comorbid condition or cause of ESRD) were considered high risk.

Mean age (+/− SD)70 (4)70 (4)69 (3)<0.001
Male sex (%)606965<0.001
Race (%)   <0.001
White747666 
Black191825 
Other769 
Comorbid conditions (%)   <0.001
Ischemic heart disease 4231 
Congestive heart failure 3632 
Peripheral vascular disease 1315 
Cerebrovascular disease 98 
Diabetes as only risk factor NA10 
Cause of ESRD (%)   <0.001
DiabetesNANA79 
Hypertension414912 
Glomerular24224 
Polycystic disease1082 
Other25213 
Year of waiting list (%)   <0.001
1995–1999232418 
2000–2004454645 
2005–2007323237 
Table 2. Use of standard criteria, expanded criteria and living donor transplantation by the patient cardiovascular risk group
 Low riskIntermediate riskHigh risk
 N = 5825N = 1397N = 3850
SCD N (%)2627 (45%)638 (46%)1760 (46%)
Median waiting time1.1 years1.0 years1.1 years
% Preemptive1154
ECD N (%)1713 (29%)425 (30%)1210 (31%)
Median waiting time1.2 years1.1 years1.1 years
% Preemptive942
Living donor N (%)1485 (25%)334 (24%)880 (23%)
Median waiting time0.49 years0.45 years0.49 years
% Preemptive281612

Figure 1 shows the multivariate adjusted risk of death in transplant recipients of LD, SCD and ECD kidneys compared to patients of similar cardiovascular risk who remained on the waiting list. In all patient risk groups, the risk of death in transplant recipients compared to wait-listed patients varied with time after transplantation (Figure 1). In all patient risk groups, the risk of death was highest in ECD recipients, followed by SCD and LD recipients. Living donor transplantation was associated with an immediately lower risk of death compared to treatment with dialysis in low risk and intermediate risk patients (Figure 1). In all patient risk groups, the death rate in the first year after transplantation was lowest in LD recipients, followed by SCD and ECD recipients (Table 3). The time to equal risk, and time to equal survival in transplant recipients compared to patients of similar risk who remained on dialysis, was related to donor source (Table 3). LD transplantation was associated with an immediately lower risk of death in low risk and intermediate risk patients, and an equal risk of death after 43 days and equal survival after 130 days in high-risk patients. In comparison the times to equal risk and equal survival were longer in SCD recipients, with the longest times observed in ECD recipients (Table 3). Table 4 shows the time to equal risk, and equal survival by tertile of KDRI among deceased donor recipients. Recipients of the lowest tertile KDRI transplants had the lowest time to equal risk of death, and the lowest time to equal survival.

Table 3. Death rate, days to equal risk of death and days to equal survival by donor type and patient cardiovascular risk group
Low-risk patients
Death rate on waiting list/100 patient years14
 SCDECDLD
Death rate/100 patient years during first posttransplant year8103
Days to equal risk9095Immediately lower risk
Days to equal survival203264Immediately higher survival
Intermediate risk patients
Death rate on waiting list/100 patient years17  
 SCDECDLD
Death rate/100 patient years during first posttransplant year9143
Days to equal risk96110Immediately lower risk
Days to equal survival285470Immediately higher survival
High risk patients
Death rate on waiting list/100 patient years22  
 SCDECDLD
Death rate/100 patient years during first posttransplant year11166
Days to equal risk11018043
Days to equal survival368521130
Table 4. Days to equal risk of death and days to equal survival by tertile of the kidney donor risk index
Low-risk patients
 KDRI <1.05KDRI 1.05–1.51KDRI >1.51
Days to equalImmediately61102
 riskLower risk  
Days to equalImmediately178365
 survivalHigher survival  
Intermediate risk patients
Days to equalImmediately75175
 riskLower risk  
Days to equalImmediately185435
 survivalHigher survival  
High-risk patients
Days to equal risk8295181
Days to equal survival225302525
image

Figure 1. The multivariate adjusted relative risk of death in low (first panel), intermediate (second panel) and high (third panel) cardiovascular risk patients. In each panel the multivariate adjusted risk of death in living donor (LD, shown in red), standard criteria deceased donor (SCD, shown in purple), or expanded criteria deceased donor (ECD, shown in green) transplant recipients is compared to that in wait-listed patients of similar cardiovascular risk (shown in blue) who had been on dialysis for equal lengths of time but who had not yet received a kidney transplant. In all cardiovascular risk groups, the risk of death immediately after SCD and ECD transplantation was higher than that among wait-listed patients of similar cardiovascular risk. In contrast, the risk of death in low and intermediate cardiovascular risk recipients was immediately lower than that in similar risk patients who remained on the waiting list. The long-term risk of death was lower with transplantation in all risk groups and with all donor types.

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The donor-related differences in death rate, days to equal risk and days to equal survival also varied by recipient risk: The smallest differences were observed in low-risk patients with larger differences in intermediate and high-risk patients (Table 3).

Discussion

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

Quantification of the early risk of death in elderly transplant recipients from different donor sources in this study may be useful to care providers when counseling patients about their transplant options. The study demonstrates that despite significant efforts to minimize the early risks of deceased donor transplantation, this risk remains a barrier to transplantation for elderly patients. The study shows that living donor transplantation is the safest strategy to increase transplantation in this patient group, and the results should help expand the use of living donor transplantation in ESRD patients ≥ 65 years. The relevance of these findings may increase in the future because proposed changes to the deceased donor kidney allocation in the United States may limit opportunities for SCD transplantation in this age group [5]. Finally the study confirms the importance of DGF as a risk factor for early mortality and suggests that strategies to reduce DGF could improve early survival in elderly patients [6].

In low cardiovascular risk patients, LD transplantation was associated with an immediate survival advantage compared to dialysis; however, the greatest risk reduction was seen in intermediate cardiovascular risk patients where the time to equal survival was reduced from 470 days with an ECD transplant to zero days with a LD transplant. Although LD transplantation was associated with an increase in early mortality in high cardiovascular risk patients, the risk reduction as quantified by the time to equal survival (reduced from 521 days with an ECD transplant to 130 days with a living donor transplant) was still greater than that observed in low-risk patients (time to equal survival reduced from 264 days with an ECD transplant to zero days with a living donor transplant). These findings should help address concerns regarding the use of living donors in elderly transplant candidates with a history of cardiovascular disease. However, the excess early mortality after living donor transplantation in high-risk patients remains an important consideration that should be discussed with patients and their potential donors.

Although the likelihood of transplantation among the elderly increased twofold over the last decade, only 7% of ESRD patients ≥ 65 years are transplanted after 3 years of dialysis initiation [7]. In part this is due to high mortality on the waiting list, with a recent analysis demonstrating that the 5-year probability of deceased donor transplantation in patients aged ≥ 65 years is nearly equal to the probability of death on the waiting list [8]. Despite these statistics, many elderly patients and their care providers may be reluctant to pursue living donation. Offspring to parent donations account for only 1.5% of living donor transplants among recipients > 55 years [9], suggesting a reluctance to proceed with living donor transplantation when there is a significant difference in donor and recipient age. Younger patients may be more willing to accept living donation [10], but few studies have specifically examined the acceptance of living donation in elderly patients, or the willingness of individuals to donate to older patients.

It is important to recognize that although our findings favor the use of living donation in the elderly, transplantation from any donor source was associated with a reduced long-term risk of death compared to treatment with dialysis. Nonetheless the quantification of the time to equalize risk and to equalize survival compared to continued treatment with dialysis may be used to counsel some high-risk patients to only consider transplantation from a living donor. Therefore it is important to note that elderly patients in this study received deceased donor transplants after a median waiting time of only 1.0–1.2 years and it may take longer to equalize risk and survival in patients with longer waiting times. Similarly, we did not include deaths after removal from the waiting list, because we could not verify the indications for wait-list removal. Inclusion of deaths after delisting would likely decrease the time for the risk of death and survival to equalize between transplant recipients and wait-listed patients.

The study highlights the perioperative and early posttransplant period as a barrier to transplantation in elderly patients who could derive a long-term survival advantage if they could be successfully transplanted. Cardiovascular disease is the leading cause of death during the early-posttransplant period [11]. Previous studies have highlighted the importance of coordinated care between dialysis and transplant physicians in order to optimize the medical management of cardiovascular risk factors in wait-listed candidates [12]; however, no strategy or intervention has been shown to reduce cardiovascular mortality during the early-posttransplant period [13]. To date most studies have focused on identification of high-risk transplant candidates, and strategies to monitor and maintain the medical fitness of wait-listed patients, but no studies have specifically proposed donor selection as a strategy to minimize early posttransplant risk. The finding that wait-list removals were identical among low, intermediate and high-risk patients despite difference in wait-list mortality highlights the need to develop protocols for systematic reevaluation and wait-list removal of transplant candidates with a decline in health status during wait listing.

This study uses similar methods employed by Wolfe and colleagues [1] and extends those findings by providing more current information that is specific to the elderly population, and by quantifying risk with transplantation from different donor sources. The study by Wolfe and colleagues included only about 3000 deceased donor recipients ≥ 60 years. The estimation of time to equal risk and equal survival in this study was determined in transplant recipients compared to similar risk patients who remained on the waiting list and differs from that in the study of ECD transplantation by Merion and colleagues [14]. In that analysis outcomes after ECD transplantation were compared with continued waiting on the deceased donor waiting list and transplantation from a standard criteria deceased donor. As a result the times to equal risk and equal survival among ECD recipients in the Merion study are longer than those among ECD recipients in this study.

Readers of this study should be aware of the inherent limitations of observational studies and the limitations of secondary analyses of registry data. Although our multivariate analyses adjusted for differences in a variety of factors that impact transplant outcome, there are undoubtedly unaccounted differences between LD, SCD and ECD recipients in this study that may confound our findings. Although the study included all elderly transplant recipients in the United States, the results may be difficult to apply to individual patients. The classification of cardiovascular risk in this study is not validated. Cardiovascular risk was classified based on history of comorbidities recorded at the time of first treatment for end-stage renal disease and does not include assessment of the severity of individual comorbid conditions.

In summary, the quantification of the early risk of transplantation from different donors sources in this study demonstrates that LD transplantation is the safest transplant option for elderly patients. These findings may be useful in counseling elderly patients about their transplant options, and may help expand the use of living donation in this patient group. The findings also highlight the need for strategies to minimize the early risk of mortality in the elderly.

Acknowledgments

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

The data reported here have been supplied by the United States Renal Data System (USRDS). The interpretation and reporting of these data are the responsibility of the author(s) and in no way should be seen as an official government policy or interpretation of the US government.

C.R. is supported by the Kidney Research Scientist Core Education and National Training Program.

Disclosure

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References

The authors of the manuscript have no conflicts of interest to disclose as described by the American Journal of Transplantation.

References

  1. Top of page
  2. Abstract
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Acknowledgments
  8. Disclosure
  9. References