Long-term Outcome Reporting in Older Kidney Transplant Recipients and the Limitations of Conventional Survival Metrics

INTRODUCTION: The kidney transplant recipient population in the United States is aging rapidly, which may exacerbate some of the limitations of conventional outcome metrics. METHODS: Using data from the Scientific Registry of Transplant Recipients (SRTR), age-stratified unadjusted Kaplan-Meier and competing risk survival analyses were performed on a cohort of 238,123 adult recipients of a first-time single kidney transplant between 2000 and 2017. These were compared with a multistate model incorporating 5 post-transplant states (alive with functioning graft, death with functioning graft, graft failed (alive), retransplanted, and death after graft failure). RESULTS: Kaplan-Meier resulted in an age-dependent overestimation of the risks of graft failure and death with functioning graft, compared with competing risk or multistate models. In elderly (≥75 years old) recipients, the absolute overestimation of the risk of death with functioning graft was 4-fold higher than in those younger than 55 years. The multistate model demonstrated that for patients transplanted at age 55 years and older, the probability of being back on dialysis was never more than 4% at any point post-transplant. The underlying reasons were low graft failure rates and high mortality after resuming dialysis as follows: 2-year mortality after graft failure was 38%, 54%, and 67% in recipients aged from 55 to 64 years, from 65 to 74 years, and those aged 75 years and older, versus 20% in those younger than 55 years. CONCLUSION: Multistate models provide an accurate and comprehensive assessment of the life course of kidney transplant recipients. This may be particularly relevant in older recipients, who are more prone to event rate overestimation and for whom outcomes after graft failure are substantially worse than for younger recipients.