Elevated Early Mortality with the Novel Composite Allocation Score in Lung Transplantation: Too Soon to Tell or Harbinger of Future Challenges?

R. Asija¹, R. Singh², S. A. Brownlee³, C. Chukwudi², A. Kreso², S. Rabi², E. Michel⁴, N. B.. Langer⁵, A. A. Osho^2
1Community Memorial Health Systems, VENTURA, California ²Massachusetts General Hospital, Boston, Massachusetts ³Massachussetts General Hospital, Boston, Massachusetts ⁴Massachusetts General Hospital, Somerville, Massachusetts ⁵Massachusetts General Hospital, Wellesley, Massachusetts

Purpose: The Composite Allocation Score (CAS) for lung transplantation was implemented in March 2023 with anticipated improvements in post-transplant mortality. In this study, we contrast rates of early mortality in lung recipients during the early CAS era with rates in lung recipients during the Lung Allocation Score (LAS) era.

Methods: The OPTN database as of June 30, 2023 was queried for first-time adult lung transplant recipients from November 1, 2022, to June 30, 2023 to examine cohorts immediately before and after the CAS allocation system change. The LAS era was defined as the period before March 9, 2023 and the CAS era was defined as March 9, 2023 and after. Multi-organ transplants and re-transplants were excluded from the study. The primary outcome of 30-day mortality was assessed using Kaplan-Meier curves and univariable Cox regression modeling. Secondary outcomes including acute rejection, extracorporeal membrane oxygenation (ECMO) requirement at 72 hours, and ventilator support at 72 hours were assessed using logistic regression modeling.

Results: One thousand nine hundred twenty-four adult lung recipients met inclusion criteria during the study period, of which 967 (50.3%) of these patients were transplanted during CAS era while 957 (49.7%) were transplanted during the LAS era. CAS era patients were generally younger (62 vs. 63, p< 0.001), and received lungs with longer ischemia times (6.7 hours vs. 6.1 hours, p< 0.001). There was a trend towards higher early mortality in lung transplant recipients during the CAS era as compared to those transplanted during the last few months of the LAS era (3.7% vs 2.3%; HR 1.9, 95% CI 0.98-3.5, p=0.055). There was no difference in acute rejection (p=0.53), post-operative need for ECMO (p=0.51) or post-operative need for the ventilator (p=0.53) when comparing recipients in the CAS era to recipients in the LAS era.

Conclusion: The demonstrated trend of increased 30-day mortality in CAS lung transplant recipients contradicts the expectation of improved post-transplant survival with CAS score implementation. While early, these findings highlight the need for consistent and systematic evaluation of the impact of this novel lung transplant allocation system on recipient outcomes.

Identify the source of the funding for this research project: None