Increasing Access to Lung Transplant Through Changes in Donor Lung Allocation

By Wayne Tsuang, MD MHS, and Maryam Valapour, MD MPP

Lung transplantation remains the definitive treatment for end-stage lung diseases, with the number of lung transplants in the United States reaching an all-time high of 1,946 in 2013. Leading indications for transplant include pulmonary fibrosis, chronic obstructive pulmonary disease, cystic fibrosis and pulmonary hypertension. Despite the increase in the number of transplants, the number of organ donors is outpaced by the number of patients on the waiting list. Therefore, our research efforts are focused on the efficient utilization and distribution of available organs.

How U.S. lung allocation works

The geographic location of an organ donor is a major criterion for allocation. Organs are first offered to nearby, or “local,” wait-listed patients prior to being offered to a wider region. “Local” is defined as within the donation service area (DSA) administered by an organ procurement organization. There are 58 DSAs in the United States with boundaries that were determined in the early years of transplant mainly in light of ischemic time. If no wait-listed candidates within the boundaries of the DSA are identified, the donor lungs are offered beyond the local DSA in 500-mile-radius increments from the donor’s location until the organ is accepted.

Another major criterion for organ distribution is donor age, which determines the priority of patient age groups eligible to receive the organs within each geographic area. Patient age groups are defined as adults ≥ 18 years of age, adolescents 12 to 17 years, and children < 12 years. Adult donor lungs are first offered to adults or adolescents, and then children, within the local area. Adolescent donors lungs are first offered to adolescents, and child donor lungs are first offered to children before the other age groups are considered.

Only after using the donors’ geographic location and age to identify a cohort of wait-listed patients are additional clinical criteria used. These criteria include ABO blood type, thoracic size, immunologic compatibility and Lung Allocation Score (LAS). The LAS was implemented in 2005 and is a weighted score that incorporates both medical urgency (estimated survival without transplant) and transplant benefit (difference between estimated survival with and without transplant). The score ranges from 0 to 100 and the higher the score, the higher the priority for transplant. The LAS applies to adult and adolescent wait-listed patients; children on the waiting list are prioritized as status 1 or 2 depending on clinical data and time accrued on the waiting list.
Studying alternative algorithms for pediatric patients

The U.S. organ allocation systems are designed to prioritize wait-listed pediatric patients (adolescents and children) for transplant, thereby minimizing the impact of end-stage organ disease on their life span and quality of life. But does the current system for lung transplant do this adequately?

This question was raised during a recent national controversy involving an 11-year-old patient with cystic fibrosis. This patient, and a dozen other similarly aged patients who followed, were permitted to seek simultaneous access to adult, adolescent and child donors. However, this measure has not been as effective as hoped; very few wait-listed children successfully matched with an adolescent or adult donor due to thoracic size considerations.

Improving access for pediatric patients

Ideal strategies to increase lung transplant rates for pediatric patients require improving access to pediatric donors. Recent research in liver transplant showed that broader geographic sharing of donor livers increased transplant rates for the highest acuity wait-listed patients. We applied the principles of broader geographic sharing to the pediatric lung population by modeling alternative geographic boundaries for organ allocation. For example, current allocation rules require that adolescent donor lungs be allocated locally first to adolescents, then to children and then to adults. In a recent study published in the American Journal of Transplantation, we showed that if the same adolescent donor lungs are offered more broadly first to wait-listed children and then adolescents within a 1,000-mile radius before local wait-listed adults are considered, both the child and adolescent transplant rates will potentially increase without adversely impacting the adult transplant rates.

The simulation models and their results, which were developed by the Scientific Registry of Transplant Recipients for the Organ Procurement and Transplantation Network (OPTN), the government organization charged with establishing and maintaining U.S. transplant policy, are under review as possible alternatives to the current U.S. lung allocation policy.

In addition to this project, we are engaged in ongoing research to define the impact of expansion of recipient and donor selection criteria on lung transplant outcomes, and alternative lung allocation models to improve patient access, outcomes and quality of life.
Wayne Tsuang, MD MHS, is is a member of the Lung Transplantation section and Department of Critical Care Medicine. He can be reached at 216.445.6448 or tsuangw@ccf.org. Maryam Valapour, MD MPP, is Director of Lung Transplant Outcomes at the Respiratory Institute. She can be reached at 216.445.4071 or valapom@ccf.org.