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Kidney Week

Abstract: PO2105

Survival Time Gained by Kidney Transplantation Compared to Remaining Waitlisted on Dialysis: A National Registry Study Using Target Trial Emulation

Session Information

Category: Transplantation

  • 1902 Transplantation: Clinical

Authors

  • Haller, Maria C., Medical University of Vienna, Center for Medical Statistics, Informatics and Intelligent Systems, Section for Clinical Biometrics, Vienna, Austria
  • Wallisch, Christine, Medical University of Vienna, Center for Medical Statistics, Informatics and Intelligent Systems, Section for Clinical Biometrics, Vienna, Austria
  • Strohmaier, Susanne, Medical University of Vienna, Center for Medical Statistics, Informatics and Intelligent Systems, Section for Clinical Biometrics, Vienna, Austria
  • Kammer, Michael, Medical University of Vienna, Center for Medical Statistics, Informatics and Intelligent Systems, Section for Clinical Biometrics, Vienna, Austria
  • Heinze, Georg, Medical University of Vienna, Center for Medical Statistics, Informatics and Intelligent Systems, Section for Clinical Biometrics, Vienna, Austria
  • Oberbauer, Rainer, Medical University of Vienna, Department of Medicine III, Division of Nephrology and Dialysis, Vienna, Austria
Background

It is widely taken for granted that kidney transplantation improves survival compared to remaining on dialysis. However, the previous evidence based on cohort studies is at high risk of bias and randomized controlled trials are not feasible.

We aimed to investigate survival differences of kidney transplantation compared to remaining waitlisted on dialysis across different transplant candidate ages as well as depending on waiting time applying causal inference methodology.

Methods

We included all dialysis patients recorded in the Austrian Dialysis and Transplant Registry who were waitlisted for their first kidney transplant between 2000 and 2018 and utilized repeated updates on waitlisting status and relevant covariates.
To estimate causal effects of kidney transplantation across ages, we specified a target trial protocol mimicking a series of controlled clinical trials initiated at the ordered times of transplantation relative to waitlisting. At each trial in the series patients were classified as either treated (transplanted) or control (remained on waitlist). We estimated restricted mean time gained by transplantation using sequential Cox regression adjusted for confounding and adherence to the treatment strategy by inverse probability weights for treatment and censoring, and stratified our analysis by pre-transplant waiting time (up to 1 year, 1 to 2 years, more than 2 years).

Results

4445 patients were included, 33% were women, mean age was 50 years. 3621 patients (81%) were transplanted, 1392 patients died.
Transplanted patients had longer 5- and 10-year restricted mean survival times compared to patients remaining waitlisted across all ages. E.g. a patient aged 70 at transplantation gained 0.85 years within 5 years posttransplant. Stratified analyses showed a gain of 0.61 years conditional on having been waitlisted up to 1 year and 0.82 and 1.35 years conditional on having been waitlisted for 1 to 2 years or more than 2 years respectively.

Conclusion

Our study provides evidence based on state-of-the-art causal inference methodology for moderately increased survival after kidney transplantation in the elderly and irrespective of time on waiting list.