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

In 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.

A retrospective cohort study was conducted using the United Network for Organ Sharing database, queried for adult lung transplants from September 1, 2022 to September 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.

A total of 1,394 pre-CAS and 1,197 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 traveled significantly further (354.0 miles [interquartile range (IQR): 139-657] vs 195.0 miles [IQR: 78-388], p < 0.001). CAS patients had longer ischemic times (6.8 hours [IQR: 5.3-8.9] vs 6.0 hours [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 the 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.

The 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.