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

Purpose: On March 9, 2023, the Composite Allocation Score (CAS) was introduced for all lung transplantation (LT) candidates. We analyzed waitlist and post-transplant outcomes following CAS implementation. Methods: Using the UNOS registry (2022–2024), adult patients listed for isolated LT were divided into Era 1 (pre-CAS: 3/1/2022–3/8/2023) and Era 2 (post-CAS: 3/9/2023–9/30/2024). 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. Results: Among 6,398 LTs, 2,598 (40.6%) occurred in Era 2. More Black patients (16.9% vs. 15%, p=0.04) and those with a high school education (35.4% vs. 33.4%, p=0.0003) were transplanted. ABO type O patients were less likely to undergo LT (42.5% vs. 46.6%, p=0.04). Era 2 had longer transport distances (231 vs. 202 miles, p<0.0001), ischemic times (5.1 vs. 4.9 hours, p<0.0001), and increased use of flights (79.1% vs. 72.8%, p<0.0001). DCD (9.4% vs. 6.2%, p<0.0001) and NRP (2.2% vs. 1.2%, p=0.02) usage rose. Waitlist times decreased (29 vs. 31 days, p=0.009), with improved outcomes (SHR 0.73, p<0.0001). Era 2 showed superior 6-month and 1-year survival (p<0.0001) and reduced rejection treatment (2.6% vs. 14.5%, p<0.0001). Conclusions: CAS implementation reduced waitlist mortality, improved access for marginalized groups, and enhanced survival. Lungs were procured from greater distances with increased use of DCD with NRP or ex vivo perfusion. Disparities remain for ABO type O patients, warranting closer follow-up.