Validation of a novel donor lung scoring system based on the updated lung composite allocation score (CAS)

Lung transplantation continues to have lower rates of long-term graft survival compared to other organs. Additionally, lung utilization rates from brain-dead donors (BDDs) remain substantially lower compared to other solid organs, despite a growing need for lung transplantation and significant risk of waitlist mortality. This study aims to examine the effects of using a combination of the recently described novel lung donor acceptability score (LUNDON) and the newly adopted recipient lung composite allocation score (CAS) to guide transplantation. We performed a review of nearly 18000 adult primary lung transplants from 2015-2022 across the US with retroactive calculations of the CAS score. The medium CAS group (29.6-34.5) had superior 1-year post-transplant survival. Importantly, the combination of high CAS (>34.5) recipients with low LUNDON score (≤40) donors had the worst survival at 1 year compared to any other combination. Additionally, we constructed a model that predicts 1-year and 3-year survival using the CAS and LUNDON scores. These results suggest that caution should be exercised when using marginally acceptable donor lungs in high priority recipients. The use of the LUNDON score with CAS can potentially guide clinical decision-making for optimal donor-recipient matches for lung transplantation.