The Dawn of the Composite Allocation Score: Travel Distances Doubled to Deliver Lungs to Healthier Recipients

R. Singh¹, R. Asija², S. A. Brownlee³, D. M. Giao¹, S. Rabi¹, E. Michel⁴, B. C. Keller¹, A. A. Osho¹, N. B.. Langer^5
1Massachusetts General Hospital, Boston, Massachusetts ²Community Memorial Health Systems, VENTURA, California ³Massachussetts General Hospital, Boston, Massachusetts ⁴Massachusetts General Hospital, Somerville, Massachusetts ⁵Massachusetts General Hospital, Wellesley, Massachusetts

Purpose: The Organ Procurement and Transplant Network (OPTN) developed the Composite Allocation Score (CAS) to improve survival following lung transplantation and increase geographical equity. In this study, we compare characteristics of recipients in the dawn of the CAS era to the twilight of the Lung Allocation Score (LAS) period.

Methods: Adult recipients of single and double lung transplants were identified between November 1, 2022 to June 30, 2023 using the OPTN data as of June 30, 2023. Multi-organ transplants and re-transplants were excluded. LAS era was defined as the time period before March 9, 2023 and the CAS era was defined as March 9, 2023 and after. Recipient and donor transplant characteristics were assessed using Wilcoxon’s Rank Sum test for continuous non-normal variables. Chi-squared test or Fisher’s Exact test were used as appropriate for categorical variables. Statistical significance was defined as p-value less than 0.05. Statistical analysis was performed using SAS 9.4 (SAS Institute Inc, Cary, NC).

Results: A total of 1,924 lung recipients were included in the study, of which 967 received organs allocated through CAS and 957 through LAS. The median LAS score was 41.1 (36.1-53.1), and the median CAS score was 30.4 (29.1-34.0). Transplant recipients in the CAS era were younger in age (62 years vs. 63 years, p< 0.001) and more likely to be in the ICU at time of transplant (19.8% vs. 15.3%, p=0.03) but less likely to be intubated (1.9% vs. 4.2%, p=0.003) or be on extracorporeal membrane oxygenation (ECMO) at the time of transplant (2.6% vs. 6.4%, p< 0.001). Patients transplanted during the CAS era had longer ischemia times (6.7 hours vs. 6.1 hours, p< 0.001) and were less likely to have an ABO identical match to the donor (81.8% vs. 90.6%, p< 0.001). Most significantly, the distance traveled to retrieve donor lungs for recipients transplanted using the CAS score was much greater than for recipients listed under the LAS score (347 miles vs. 195 miles, p< 0.001).

Conclusion: Our findings are consistent with a priori predictions about the impact of this policy prioritizing younger, healthier patients while significantly expanding procurement geography. Further studies will be needed to understand the patient outcomes, cost and logistical implications of a more nationwide donor pool.

Identify the source of the funding for this research project: None