The Impact of Composite Allocation Score Implementation on Waitlist Outcomes and Post-Transplant Survival in Lung Re-Transplantation.

BACKGROUND

The Lung Composite Allocation Score (CAS) was implemented in March 2023. While early evaluations showed no adverse effect of CAS on short-term survival for primary transplants, its impact on re-transplantation remains unknown.

METHODS

We identified all adult patients from the United Network of Organ Sharing database who underwent lung transplantation between January 2017 and March 2025. The primary outcomes were one-year post-transplant survival compared between primary and re-transplant recipients and one-year post-transplant survival among re-transplant recipients compared across three eras: Era 1 (2017-2019), Era 2 (2020-March 9, 2023), and Era 3 (CAS, March 9, 2023-March 2025).

RESULTS

Among 21,569 patients, 665 (3.1%) underwent re-transplantation. Compared to primary transplants, re-transplant recipients required more pre-operative ECMO (8.7% vs 3.6%, p<0.001) and more ventilator support (11.4% vs 2.7%, p<0.001). Re-transplants had significantly worse 1-year survival (79.3% [75.9-82.3] vs 89.2% [88.7-89.6], aHR 2.18 [1.79-2.64], p<0.001). Among re-transplants, there were no differences in 1-year survival across eras (Era 1: 79.4% [73.4-84.2]; Era 2: 79.1% [73.5-83.7], aHR 0.96 [0.63-1.45], p=0.85; Era 3: 80.1% [72.4-85.9], aHR 0.70 [0.42-1.17], p=0.18). The waitlist times across eras were similar (p=0.28). However, Era 3 recipients had longer donor travel distances and longer donor ischemic times (both p<0.001). There were no differences in waitlist mortality or transplant rates for re-transplants between eras (p>0.05).

CONCLUSIONS

Re-transplant rates, waitlist times, and one-year survival were unchanged across eras. However, the limited CAS-era cohort precludes conclusions regarding equivalence, and larger studies with longer follow-up are needed.