Background: Comparison of mortality rates after kidney transplantation with those treated by dialysis is an important factor is assessing treatment options, but is subject to many pitfalls in selection of appropriate control groups, in particular allowing for varying post-operative risk, and recent changes in mortality rates with better immunosuppression and dialysis techniques. We examined the outcomes following cadaveric renal transplantation and compared them with an appropriate control group of dialysis patients, using contemporary national data from Australia and New Zealand and appropriate statistical methods. In particular, we explicitly addressed the changing risks following transplantation, and looked at both younger (low-risk) and older (higher-risk) recipients, and examined the effect of attribution of deaths in the early period following loss of transplant function to the risk of transplantation.
Methods: We performed a cohort study, initially including 11 560 people aged 15-65 years who began treatment for end-stage renal disease in Australia or New Zealand between 1991 and 2000. Of these, 5144 were recorded at least once as on an active cadaveric transplant waiting list. Survival was analysed with Cox regression, including time-dependent covariates to allow for the violation of proportional hazards with changing mortality risks post-operatively. We also performed stratified analyses on low-risk recipients (<50 years, without co-morbidity) and older recipients.
Results: There was a clear difference in survival between those on the active transplant waiting list and those not listed. Of those who were on the cadaveric transplant waiting list, 2362 (46%) were transplanted in the period to 30 September 2001. Cadaveric transplantation was associated with an initial increase in mortality [during the first 3 months post-transplantation, adjusted HR 2.0 (1.5-2.7), P<0.001]. This fell below the dialysis group at 6 months [adjusted HR 0.27 (0.16-0.47), P<0.001] and from 12 months post-transplantation, the reduction in risk of mortality was approximately 80% [adjusted HR 0.19 (0.15-0.24), P<0.001]. A secondary analysis showed the excess risk attributed to the period immediately following transplantation was actually due to deaths in the 60 days after loss of transplant function rather than those occurring with a functioning graft.
Conclusions: As well as improved quality of life, cadaveric renal transplantation in Australia and New Zealand is associated with a survival advantage compared with those remaining on the waiting list.