Bridging Oceans and Distance: Excellent Long‐Term Outcomes in Non‐Mainland Kidney Transplantation

PURPOSE: Efforts to expand the kidney transplant (KT) donor pool have included geographic expansion of donation. We evaluated the outcomes after KT from organs procured outside of the continental United States (US). METHODS: Adult kidney-only deceased donor transplants from 2011 to 2022 in the United Network for Organ Sharing (UNOS) database were categorized by donor and recipient location (mainland to mainland US [MM], non-mainland to mainland [NMM], and non-mainland to non-mainland [NMNM]). Recipient overall and event-free survival were evaluated using time-to-event analysis and multivariable Cox regression. RESULTS: There were 163 004 (98.5%) MM, 1351 (0.8%) NMM, and 1190 NMNM (0.7%) transplants, with non-mainland donors from Puerto Rico (1233), Hawaii (806), Alaska (483), Bermuda (12), and the United States Virgin Islands (USVI) (7). Non-mainland donors were older (p < 0.001), had lower body mass index (BMI) (p < 0.001), were less likely to have smoked cigarettes (p < 0.001), had lower creatinine (p < 0.001), and were less likely to donate after cardiac death (p < 0.001) or utilize perfusion machines (p < 0.001) compared to MM. NMM transplants traveled further between donor and recipient centers (p < 0.001) and had longer cold ischemia times (CITs) (24.1 vs. 17.2 h, p < 0.001). There was no difference in acute rejection (adjusted odds ratio [aOR] 1.14, p = 0.59). NMM recipients had similar 1-year (adjusted hazard ratio [aHR] = 0.87 [95% confidence interval (CI) 0.65-1.15], p = 0.32) and 5-year (aHR = 0. 90 [95% CI 0.77-1.06], p = 0.19) event-free survival and improved survival at 10 years (aHR = 0.83 [95% CI 0.72-0.95], p = 0.006) post-transplant. CONCLUSION: Despite longer distances and CIT, select kidneys from NM donors can be successfully transplanted with excellent long-term outcomes, including improved event-free survival at 10 years post-transplant. Use of NM donors should be encouraged to increase rates of KT.