Call for Changes in Lung Allocation to Reduce Transplant Wait-List Mortality for Cystic Fibrosis

Lung Allocation Score Exceptions in Persons with Cystic Fibrosis Undergoing Lung Transplant

Rationale: Lung transplantation can extend the lives of individuals with advanced cystic fibrosis (CF). Until March 2023, the Lung Allocation Score (LAS) was used in the United States to determine transplant priority. Certain clinical events or attributes ("risk events") that are not included in the LAS (e.g., massive hemoptysis) are relatively common and prognostically important in CF and may prompt an exception request to increase priority for donor lungs. The new Lung Composite Allocation Score (CAS) also allows for exceptions based on the same principles. Objectives: To evaluate the frequency of LAS exceptions in persons with CF (PwCFs) listed for lung transplantation and assess whether LAS exceptions are associated with improved waitlist outcomes for PwCFs compared with similarly "at-risk" individuals without LAS exceptions. Methods: A merged dataset combining data from the CF Foundation Patient Registry and the Organ Procurement and Transplantation Network (2005-2019) was used to identify PwCFs listed for lung transplantation. We compared waitlist outcomes between PwCFs with a LAS exception versus those without an exception despite having a risk event. Risk events were defined as an episode of massive hemoptysis, pneumothorax, at least three moderate/severe pulmonary exacerbations, and/or a decrease in forced expiratory volume in 1 second by ⩾30% predicted (absolute) in the prior 12 months. Analyses were performed using competing risk regression with time to transplantation as the primary outcome and death without a transplant as a competing risk. Results: Of 3,538 listings from 3,309 candidates, 2% of listings (n = 81) had at least one exception. Candidates with an exception and those with a risk event but no exception received lung transplants more slowly than people without an exception or risk event (subdistribution hazard ratio [95% confidence interval]: LAS exception cohort, 0.66 [0.52-0.85]; risk event cohort without exceptions, 0.79 [0.72-0.86]). There was no difference between those with LAS exceptions and those at risk without LAS exceptions: subdistribution hazard ratio, 0.84 (0.66-1.08). Conclusions: LAS exceptions are rare in PwCFs listed for lung transplantation. LAS exceptions resulted in a similar time to transplantation for PwCFs compared with similarly at-risk individuals. As we enter the CAS era, these LAS-based results are pertinent to improve risk stratification among PwCFs being considered for lung transplantation.

Lung Transplantation in a New Era in the Field of Cystic Fibrosis

Lung transplantation for people with cystic fibrosis (PwCF) is a critical therapeutic option, in a disease without a cure to this day, and its overall success in this population is evident. The medical advancements in knowledge, treatment, and clinical care in the field of cystic fibrosis (CF) rapidly expanded and improved over the last several decades, starting from early pathology reports of CF organ involvement in 1938, to the identification of the CF gene in 1989. Lung transplantation for CF has been performed since 1983, and CF now accounts for about 17% of pre-transplantation diagnoses in lung transplantation recipients. Cystic fibrosis transmembrane conductance regulator (CFTR) modulators have been the latest new therapeutic modality addressing the underlying CF protein defect with the first modulator, ivacaftor, approved in 2012. Fast forward to today, and we now have a growing CF population. More than half of PwCF are now adults, and younger patients face a better life expectancy than they ever did before. Unfortunately, CFTR modulator therapy is not effective in all patients, and efficacy varies among patients; it is not a cure, and CF remains a progressive disease that leads predominantly to respiratory failure. Lung transplantation remains a lifesaving treatment for this disease. Here, we reviewed the current knowledge of lung transplantation in PwCF, the challenges associated with its implementation, and the ongoing changes to the field as we enter a new era in the care of PwCF. Improved life expectancy in PwCF will surely influence the role of transplantation in patient care and may even lead to a change in the demographics of which people benefit most from transplantation.

Waiting List Dynamics and Lung Transplantation Outcomes After Introduction of the Lung Allocation Score in The Netherlands

Supplemental Digital Content is available in the text.

The Netherlands was the third country to adopt the lung allocation score (LAS) for national allocation of donor lungs in April 2014. Evaluations of the introduction of the LAS in the United States and Germany showed mainly beneficial effects, including increased survival after transplantation.

A Simple Prioritization Change to Lung Transplant Allocation May Result in Improved Outcomes

BACKGROUND

The lung allocation score (LAS) significantly improved outcomes and wait list mortality in lung transplantation. However, mortality remains high for the sickest wait list candidates despite additional changes to allocation distance. Regulatory considerations of overhauling the current lung allocation system have met significant resistance, and changes would require years to implement. This study evaluates whether a modest change to the current system by prioritization of only high-LAS lung transplant candidates would result in lowered wait list mortality.

METHODS

The Thoracic Simulated Allocation Model was used to evaluate all lung transplant candidates and donor lungs recovered between July 1, 2009 and June 30, 2011. Current lung allocation rules (initial offer within a 250-nautical mile radius for ABO-identical then compatible offers) were run. Allocation was then changed for only patients with an LAS of50 or higher (high-LAS) to be prioritized within a 500-nautical mile radius with no stratification between ABO-identical and compatible offers. Ten iterations of each model were run. Primary end points were wait list mortality and posttransplant 1-year survival.

RESULTS

A total of 6538 wait list candidates and transplant recipients were evaluated per iteration, for a total of 130,760 simulated patients. Compared with current allocation, the adjusted model had a 23.3% decrease in wait list mortality. Posttransplant 1-year survival was minimally affected.

CONCLUSIONS

Without overhauling the entire system, simple prioritization changes to the allocation system for high-LAS candidates may lead to decreased wait list mortality and increased organ use. Importantly, these changes do not appear to lead to clinically significant changes in posttransplant 1-year survival.