Chest
Volume 128, Issue 1, July 2005, Pages 407-415
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Pro/Con Debate: Lung Allocation Should Be Based on Medical Urgency and Transplant Survival and Not on Waiting Time

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Pro

Thomas M. Egan, MD, MSc

Lung transplantation is an acceptable therapy with which to palliate patients with a variety of end-stage lung diseases, but there is a severe shortage of suitable donor lungs to meet the demand (Fig 1), which hinders broad application. In the last 5 years, approximately 2,500 potential lung recipients have died while on the UNOS lung transplant waiting list.1 Because of the shortage of lungs for transplantation, strict listing criteria have been espoused2; thus, the

How Should Lungs Be Allocated?

At the center of any discussion of how organs should be allocated is the controversial issue of how any scarce resource should be allocated. For most commercial items, market forces come into play, but this is arguably unacceptable for transplantation, and in the United States it is illegal under the provisions of the National Organ Transplant Act. The notion of “waiting in line” is a frequently employed method to access goods and services, and is easy to understand. Waiting in line for medical

The New Allocation System

The new lung allocation system is outlined in detail on the OPTN web site.13 Briefly, candidates listed for lung transplantation are assigned a lung allocation score (LAS) (Fig 2).

The new system continues to offer lungs to children < 12 years of age based on waiting time, because it was not possible to identify the factors associated with risk of death on the waiting list or posttransplant survival for this small cohort of patients with a diverse group of diagnoses. Because of the demonstrated

Advantages and Disadvantages of the New Algorithm

With waiting time removed from allocation consideration, there will be no reason to actively list candidates until they are ready to be transplanted. Currently, there are many patients listed to “accrue waiting time” even though their listing centers have no intention to perform transplants in them, resulting in a large number of wasted hours by transplant coordinators trying to place lungs. The turn-down rate for lung offers is higher than that for any other solid organ. Using risk of death on

The Future

A key feature of the new algorithm is the requirement to perform new analyses every 6 months to continually improve the algorithm. Thus, the algorithm is not “fixed in stone” but is intended to be dynamic and to adapt to the population of patients currently being listed and undergoing transplantation. A long-term goal is the ability to incorporate data on QOL into the algorithm, but reliable QOL data on lung transplant candidates and recipients were not available for analyses. The relative

Con

Robert M. Kotloff, MD, FCCP

Prediction is very difficult, especially about the future.

Niels Bohr (Nobel Laureate in Physics)

For the past 15 years, lung allocation in the United States was based on a seniority system that prioritized candidates on the basis of the amount of time they had accrued on the waiting list. The system was easily understood, based on a simple and objective parameter (time), and was relatively resistant to manipulation. However, the system was called into question because

The Need for Validation

The new model, which is derived from a multivariate analysis of data from the comprehensive United Network for Organ Sharing (UNOS) national database, identifies 10 factors that are independently predictive of death on the wait list and seven factors that are predictive of death following transplantation. For each patient, these factors are utilized in a complex set of computations that result in a prediction of the exact number of days the patient is expected to live during an additional year

Previous Experience With Predictive Models of Lung Disease

Based on the experience to date with prognostic models for predicting the natural history of various lung diseases, there is every reason to be skeptical about the validity of the lung allocation model. Space limitations preclude a full review of the literature for each disease; CF will be discussed as an example. Analyzing a cohort of 673 CF patients from the Hospital for Sick Children in Toronto, Kerem and colleagues31 published a landmark study in 1992 that identified FEV1 as the single most

Dealing With Uncommon Diseases: Should We Lump or Split?

Another aspect of the lung allocation model that engenders concern is the method chosen to handle patient populations with less common lung diseases. Having identified underlying diagnosis as a major predictor of waitlist survival, an observation that has been corroborated by multiple previous studies,223839 the model creates four major disease groups based on the leading indications for lung transplantation, as follows: COPD; primary pulmonary hypertension; CF; and idiopathic pulmonary

Defining Transplant Benefit

Finally, one must question the manner in which “transplant benefit” is defined in this model. The use of 1-year posttransplant survival is too heavily influenced by differences in disease-specific perioperative mortality rates and overlooks the fact that ultimately transplantation becomes the “great equalizer,” with all disease populations facing a similar set of long-term complications. As noted in the 2004 Report of the Registry of the International Society for Heart and Lung Transplantation,

Conclusions

Dr. Tom Egan and his colleagues on the UNOS Lung Allocation Subcommittee are to be commended for their groundbreaking efforts in developing this first iteration of a risk-stratified allocation system for lung transplantation. Unfortunately, due to pressures arising from the federal mandate to implement the new system, a step that is considered to be essential before any predictive model is considered ready for widespread clinical use has been bypassed: statistical validation.26 In the absence

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    This is the first in a series of Pro/Con Debates sponsored by the ACCP Transplant/Immunology Network designed to inform practicing pulmonologists about current controversies in lung transplantation.

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