The UNOS Composite Allocation System is Associated with Decreased 90-Day Survival

Omni King Edward Hotel 

Objective: To investigate post-operative outcomes and survival after the change in allocation policies from the lung allocation score (LAS) compared to composite allocation score (CAS).
Methods: The United Organ Sharing Database was queried from 03/08/2022 to 03/09/2024 for lung transplant recipients. Recipients were excluded if: <18 years old, re-transplants, multi-organ transplants, or had incomplete data. Recipients were then stratified into LAS (03/08/2022-03/08/2023) or CAS (03/09/2023-03/09/2024) based on date of transplant. The groups were then analyzed with comparative statistics, and Kaplan-Meier method for survival. Finally, a multivariable logistic regression using select donor and recipient characteristics was created to determine if the LAS or CAS era was independently associated with 90-day survival.
Results: There were 2925 patients stratified into the CAS group and 2648 patients stratified into the LAS group. CAS recipients were more often hospitalized prior to transplant (15% [395/2629] vs 11.9% [315/2648], p=0.001), while LAS recipients had a higher incidence of pre-operative ventilator use (5% [132/2648] vs 3.2% [93/2925], p=0.001) and ECMO use (7.3% [193/2648] vs 5.1% [148/2925], p=0.001). CAS recipients had significantly fewer days on the waitlist (median [M]: 29 days) than LAS recipients (M: 33 days) (p<0.001). CAS donors had a significantly higher incidence of smoking history (10% [282/2832] vs 7.9% [203/2555], p=0.011), higher BMI (M: 26.3 vs M: 25.9, p=0.028), and higher incidence of donation after circulatory death (DCD) donors (12.2% [356/2925] vs 7.6%, [202/2648], p<0.001) and ex vivo lung perfusion (EVLP) (8.3% [216/2606] vs 6.3% [167/2648], p=0.007). Prior to transplantation, the CAS group had a significantly longer distance traveled from donor to recipient hospital (M:382 nautical miles vs M:192 nautical miles, p<0.001) and ischemic time (M:6.8 hours vs M:5.9 hours, p<0.001). Post-operatively, the CAS group had a significantly shorter length of stay (LOS) (M:19 days vs M:20 days, p=0.002), and significantly lower incidence of primary graft dysfunction grade 3 (PGD3) (16.8% [490/2923] vs 20.7% [547/2646], p<0.001) and prolonged ventilation (5+ days) (24.1% [623/2586] vs 26.1% [685/2624], p=0.009). Additionally, the CAS group had a lower incidence of post-operative dialysis (7.9% [205/2591] vs 9.4% [250/2648], p=0.06). Neither in-hospital mortality (CAS: 4% [94/2341] vs LAS: 4.8% [125/2614], p=0.21) nor 90-day survival (CAS: 94.5% [95% confidence interval (CI), 93.5%-95.6%], LAS: 95.6% [95% CI, 94.8%-96.4%], p=0.14) was significantly different. Finally, on multivariable regression the CAS era was independently associated with decreased 90-day survival (Hazard Ratio: 0.52, 95% CI: 0.30-0.90, p=0.019).
Conclusions: In the first year following the implementation of the CAS system, CAS recipients had significantly shorter days on waitlist, and significantly lower incidence of post-operative morbidity. However, the change in the allocation system was also met with increased travel distances and ischemia time. Multivariable logistic regression found that the CAS era was independently associated with decreased 90-day survival. While the CAS change favored shorter waitlist duration, additional studies are needed to clarify the associated of the new allocation system on decreased 90-day survival.

Authors
Martin Walsh (1), Divyaam Satija* (2), Vivienne Pham (2), Ervin Cui (1), Matthew Henn (1), Kukbin Choi (1), Nahush Mokadam (1), Asvin Ganapathi (1), Doug Gouchoe (1), Bryan Whitson (1)
Institutions
(1) The Ohio State University Wexner Medical Center, Columbus, OH, (2) The Ohio State University College of Medicine, Columbus, OH