P1659SURVIVAL OF PATIENTS WAITING FOR KIDNEY TRANSPLANTATION IN TERMS OF COMPETING RISKS
Authors: Zulkarnaev Aleksei , Stepanov Vadim , Vatazin Andrey 
Published: June 2020

Abstract

Background and Aims
In Russia, when choosing a donor-recipient pair, the “waiting time” factor has very little weight. Aim: to analyze the survival of patients on the waiting list for kidney transplantation and the results of transplantation depending on the duration of waiting.

Method
We performed a retrospective observational analysis that included 1,197 patients on the waiting list. The end point was exclusion from the waiting list (WL). The causes for exclusion (death, exclusion due to deterioration of the comorbid background or transplantation) were considered in terms of competing risks.

Results
In total, 72.5% of patients reached the end point: 21.1% of them died, 11% were excluded, and 40.4% underwent transplantation. Kaplan-Meier estimate showed that cumulative risk of death was 80.4% [95% CI 77.9; 88.6], of exclusion – 77.9% [95% CI 65.4; 88.2], of transplantation – 63.6% [95% CI 58.3; 69] after 10 years on the waiting list. However, such an assessment cannot be directly interpreted as a prediction of the relevant event risk for the patient in the WL, because it does not take into account competing events.
According to a balanced assessment of the competing risks (Fine and Gray regression model), cumulative incidence was 30.9% [95% CI 27.7; 34.2] for death, 18.2% [95% CI 15.5; 21.1] for exclusion and 49.4% [95% CI 46; 52.6] for transplantation after 10 years on WL.
The probability of transplantation was significantly higher than the risk of death up to and including 5 years of waiting (incidents rate ratio – IRR 1.769 [95% CI 1.098; 2.897]). When waiting 7 to 8 years, the probability of transplantation was less than the risk of death: IRR 0.25 (95% CI 0.093; 0.588; p=0.0009) – fig 1.
Of the 483 recipients, 61 died and 119 returned to dialysis. The risk of graft loss after 10 years was 68.5% [95% CI 57.5; 79.1] and the risk of death of a recipient with a functioning graft was 48.3% [95% CI 34.7; 63] according to Kaplan-Meier estimate. The cumulative incidence was 30.8% [95% CI 23.3; 38.5] and 55.7% [95% CI 46.6; 63.5] according to Fine and Gray estimate, respectively. The risk of death after transplantation increases significantly when waiting for more than 6 years – IRR 4.325 [95% CI 1.649; 10.47], p=0.0045 relative to a shorter waiting period – fig 2.
With an increase in the waiting period, the comorbid background (CIRS scale) deteriorates significantly, even adjusted for the initial patient condition: the partial correlation r=0.735; p&lt;0.0001. The deteriorating comorbid background reduces the expediency of transplantation – fig 3 (the potential patient`s benefit is significantly reduced).
Conclusion : 1. In the context of competing risks, the Fine and Gray estimate gives a more balanced risk assessment compared to the Kaplan-Meier method.
2. Increasing the waiting time for transplantation significantly increases the risk of death of the candidate on the waiting list and reduces the probability of transplantation, as well as increases the risk of death of the recipient after transplantation. Apparently, this is mainly due to the deterioration of the comorbid background.