R. Asija1,2, R. Singh1, S. A. Brownlee1, Y. Zhao1, D. M. Giao1, A. Makarem1, G. Olverson1, C. Chukwudi1, A. A. Osho1 1Massachusetts General Hospital, Cardiac Surgery, Boston, MA, USA 2Community Memorial Health Systems, Surgery, Ventura, CA, USA
Introduction: The Composite Allocation Score (CAS) was developed and subsequently implemented in March 2023 to enhance geographical equity in lung transplantation. Prior to implementation, it was predicted that the CAS would reduce waitlist mortality in all patient populations. This analysis compares rates of waitlist mortality between patients listed during the initial three months of the CAS era and those listed during the last three months of the lung allocation score (LAS) era.
Methods: The Organ Procurement & Transplant Network (OPTN) database as of June 30, 2023 was queried for adults on the waitlist for lung transplant from November 1, 2022 to June 30, 2023. Multiorgan transplants and retransplants were excluded. The primary outcome was waitlist mortality, defined as removal from the waitlist due to death or worsening clinical condition as previously outlined in the literature. Univariable logistic regression models were used to compare the rates of waitlist mortality across eras. Statistical significance was set at a p-value less than 0.05.
Results: A total of 2,125 patients on the U.S. lung transplantation waitlist were included. Among these, 1,087 patients were listed during the CAS period and 1,038 patients were listed during the LAS period. Patients listed in the CAS period were more likely to have diabetes (19.9% vs. 17.9%, p<0.001) but less likely to require ventilator support (1.8% vs. 3.3%, p=0.036) or extracorporeal membrane oxygenation support (2.2% vs. 4.1%, p=0.011) at time of listing. The waitlist duration was shorter for patients listed in the CAS era compared to the LAS era (21 days vs. 33 days, p<0.001). The overall rate of transplantation off the waitlist was higher during the CAS era than during the LAS era (94.7% vs. 90.3%, p=0.004). Logistic regression models demonstrated lower waitlist mortality in the CAS era compared with the LAS era [23 (2.1%) vs. 49 (4.9%)]. Recipients listed in the CAS era had decreased odds of death after being listed as compared to those listed in the LAS era (OR=0.42, 95% CI: 0.26-0.70, p=0.0008).
Conclusion: This analysis of the early implications of the novel composite allocation score in lung transplantation demonstrates a decrease in waitlist mortality with the new allocation policy. Allocation of organs with fewer geographic restrictions appears to improve waitlist survival at a national level. Future studies will critically evaluate the evolution of this finding which has implications not only in lung transplantation, but also across the board in solid organ transplantation as other transplantation specialties consider transitioning to continuous allocation paradigms.
