Impact of the Composite Allocation Score on Lung Transplant Waitlist and Posttransplant Outcomes

On March 9, 2023, the Composite Allocation Score (CAS) was introduced for all lung transplantation (LT) candidates. We analyzed waitlist and posttransplant outcomes after CAS implementation.

Using the United Network for Organ Sharing registry (2022-2024), adult patients listed for isolated LT were divided into 2 eras: era 1 (pre-CAS: March 1, 2022-March 8, 2023) and era 2 (post-CAS: March 9, 2023-September 30, 2024). Competing risk regression analyzed waitlist events. Recipient/donor characteristics and mortality risk factors were assessed with Cox models. Survival was evaluated with Kaplan-Meier analysis.

Among 6398 LTs, 2598 (40.6%) occurred in era 2. More Black patients (16.9% versus 15%, P = 0.04) and those with a high school education (35.4% versus 33.4%, P = 0.0003) were transplanted. ABO type O patients were less likely to undergo LT (42.5% versus 46.6%, P = 0.04). Era 2 had longer transport distances (231 versus 202 miles, P < 0.0001), ischemic times (5.1 versus 4.9 h, P < 0.0001), and increased use of flights (79.1% versus 72.8%, P < 0.0001). Donation after circulatory death (9.4% versus 6.2%, P < 0.0001) and normothermic regional perfusion (2.2% versus 1.2%, P = 0.02) usage rose. Waitlist times decreased (29 versus 31 d, P = 0.009), with improved outcomes (sub-hazard ratio, 0.70; P < 0.0001). Era 2 showed superior 6-mo and 1-y survival (P < 0.0001) and reduced rejection treatment (2.6% versus 14.5%, P < 0.0001).

The implementation of CAS was associated with reduced waitlist mortality, improved access for marginalized groups, and enhanced survival. Lungs were procured from greater distances with an increased use of donation after circulatory death with normothermic regional perfusion or ex vivo perfusion. Disparities remain for ABO type O patients, warranting closer follow-up.