Temporal Trend and Time-Varying Effect of Preemptive Second Kidney Transplantation on Graft Survival: A 30-Year Single-Center Cohort Study

Background. There are discrepancies regarding the impact of preemptive 2nd kidney transplantation (PSKT) on graft survival. The present study aimed to determine whether the association between PSKT and outcome varies over time and whether this association is era dependent. Methods. A total of 266 patients underwent SKT (244 non-PSKT, 22 PSKT) in our center from 1985 to 2015. Association between PSKT and graft survival (allograft failure from any cause including death) was assessed with the use of Cox models. Results. During a median follow-up of 6.7 years, 116 events were recorded: 72 returns to dialysis and 44 deaths before return to dialysis. Survival curves diverged up to 5 years (5-year survivals: PSKT, 94.1 +/- 5.7%; non-PSKT, 76.8 +/- 2.9%) but they converged thereafter (12-year survivals: PSKT, 50.9 +/- 15.2%; non-PSKT, 55.5 +/- 3.9%). After adjustment for age and living-donor status, PSKT tended to be associated with better graft survival (hazard ratio [HR], 0.18; 95% confidence interval [CI], 0.02-1.27; P = .08) within the first 5 years of SKT but tended to be associated with worse outcome thereafter (HR, 2.36; 95% CI, 0.97-5.72; P = .06; P for interaction with time = .04). In addition, a significant interaction was identified between PSKT and SKT year (P for interaction = .04). In the multivariable model, the estimated HR for PSKT was 2.54 (95% CI, 0.88-7.35; P = .08) in 1990 as opposed to 0.16 (95% CI, 0.02-1.17; P = .07) in 2012. Conclusions. The effect of PSKT on graft survival varies over time and according to year of the procedure. Although the benefit observed within the first 5 years of SKT appears to fade over time, overall graft survival seemingly improved in more recent years.