Could use of long term survival in determining Lung Allocation Score improve long term outcomes in patients undergoing lung transplant?

Introduction: Allocation of organs in lung transplant is currently governed by the Lung Allocation Score (LAS), which is calculated by predicted 1-year survival benefit (1-year predicted post-transplant survival – 1-year predicted wait-list survival). Use of Lung Allocation Score has improved organ allocation and reduced wait-list duration, but the long-term survival in transplanted patients has been steady with very gradual increase despite advances in the surgical field as well as management of rejection episodes. The aim of the study was to assess if an alternative allocation method using 3-year and 5-year survival as a guide to calculate Lung Allocation Score would result in improved long term-survival along with minimal impact on wait-list mortality. Methods: Using data of all the lung transplants after implementation of LAS scores from the United Network for Organ Sharing (UNOS), predictive models for 3- and 5-year survival were created, which were used in turn to create different LAS scores (3- and 5-year survival scores as well as an equal-weight combination of 3- and 5-year survival LAS with current LAS) to assess impact of the newly created LAS scores on wait-list mortality as well as long term post-transplant survival. Results: Predicted wait-list mortality increases from 5.7% in current LAS score to 7.2% & 7.4% for equal weight 5-Year and 3-year LAS score combinations with current LAS score, which further increases to 9.0% and 9.2% for stand-alone 5-year and 3-year LAS Scores. The 5-year predicted post-transplant survival increases from 44.65% with the current LAS score to 50.44% & 50.34% with the stand-alone 5-year and 3-year LAS Scores and to 48.92% and 49.29% with the equal-weight 5-Year and 3-year LAS score combinations with current LAS score, respectively, representing almost 13% and 10% increases in 5-year predicted survival for the stand-alone and combination LAS scores. Use of long-term survival in LAS scores also predicted a consistent favoring of double-lung transplants compared to single-lung transplants. Conclusion: Use of predicted long-term survival probabilities in calculating the Lung Allocation Score may improve long-term survival; however, wait-list mortality also increases. A combination score based on long-term survival probabilities along with the current score based on predicted 1-year survival benefit may represent a good balance between increased long-term survival and increased wait-list mortality