*Purpose: Over 2,000 preemptive living donor kidney transplants (LDKT) per year are performed in the US. Preemptive LDKT allows recipients to avoid dialysis, but increases exposure to immunosuppression and burdens donors with longer exposure to nephrectomy. Most prior studies of the survival benefit of preemptive transplantation have failed to appropriately account for lead time, the unmeasured time between chronic kidney disease and transplantation. We sought to quantify the survival benefit of preemptive LDKT compared to waiting for an early LKDT (within 6 months of dialysis) after accounting for lead time bias.

*Methods: Using SRTR data, we studied 120,020 adult, preemptively listed kidney-only transplant (KT) candidates 2000-2017. To account for lead time bias, 27,839 preemptive LDKT recipients were 1:1 matched based on accumulated wait time to waitlist registrants who were dialysis-free at time of matching. Matched waitlist controls were censored 6 months after dialysis if not transplanted. We used Cox regression to compare the mortality risk between the two groups, with inverse probability weighting to account for confounding by candidate characteristics (age, sex, race, BMI, ESRD diagnosis, education, year of listing, and eGFR at listing).

*Results: Compared to waitlist controls, preemptive LDKT recipients were more likely to be younger, white, male, had lower BMI, and lower eGFR at listing. After weighting, there was no evidence of difference in mortality risk among preemptive LDKT recipients compared to waitlist controls (weighted HR: _0.84 0.92 _1.01, P=0.1, Figure).

*Conclusions: Our findings provide no evidence that preemptive LDKT is associated with a survival benefit after accounting for lead time bias. The best timing for LDKT should be determined by risks and benefits to the donor and recipient, but not only based on a perception of survival benefit.

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