Going the distance: Geographic effects of the lung transplant composite allocation score

Abstract

BackgroundIn March 2023, the lung allocation policy underwent major changes from a tiered structure to a composite allocation score (CAS). The goal was to improve allocation equity for disadvantaged groups by deprioritizing transplant distance. This study examines the effects of CAS on geographic trends and transportation efficiency. MethodsA retrospective cohort study was conducted using the United Network for Organ Sharing (UNOS) database, queried for adult lung transplants from 9/1/2022 - 9/1/2023. Outcomes were nautical distance of transplant, ischemic time, and flight required for transport (estimated as distance >100 miles). Perioperative complications and early survival were analyzed, with propensity-matching to account for baseline differences. ResultsA total of 1394 pre-CAS and 1197 post-CAS patients were included in the study cohort. Post-CAS recipients were less likely to be ABO type O (39.2% vs 47.3%, p<0.001), and were less likely to be an identical ABO match (82.7% vs. 91.0%, p < 0.001). The CAS cohort travelled significantly further (354.0 mi. [IQR:139 – 657] vs. 195.0 mi. [IQR:78 – 388], p < 0.001). CAS patients had longer ischemic times (6.8 hrs. [IQR: 5.3 – 8.9] vs. 6.0 hrs. [IQR:4.8 – 7.5], p < 0.001), and CAS procurements were more likely to require a flight for transport (n = 934, 78.0% vs. n = 991, 71.1%, p<0.001). However, waitlist time was shorter (28 days [IQR = 9 – 83] vs. 33 days [IQR = 11 – 109]) as was length of stay (24.21 ± 17.84 days vs. 31.44 ± 30.19 days, p<0.001) for CAS recipients, which remained true after propensity-matching. ConclusionThe lung CAS policy change was intended to eliminate geographic boundaries for disadvantaged patients but has expanded transplant distances, with an expected increase in ischemic time and need for flights which affect transplant economics. Although efforts were made to improve transplant availability for the disadvantaged ABO type O group, early assessment of the recipient cohort showed that recipients with blood group type O were actually less likely to be transplanted under the new policy. Positive effects include an overall decrease in waitlist time, but further investigation is warranted to evaluate the effectiveness, equity, and economic sustainability of the new policy.