By Ramsey Hachem, M.D.
Washington University School of Medicine Barnes-Jewish Hospital
Division of Pulmonary and Critical Care
June 7, 2013
Earlier this year, there was controversy in the news media about the use of lungs from donors who smoked for transplantation. The story of a young British woman with cystic fibrosis who received lungs from a smoker and died of lung cancer 16 months after her transplant made headlines and raised the seemingly obvious question of why would anyone want to have a transplant using a smoker’s lungs. However, like many controversies in medicine, the use of lungs from donors who smoked in transplantation involves a complex analysis of potential risks and benefits.
The lung donor organ shortage is the main barrier to transplantation for patients with advanced lung disease. In general, lungs are more susceptible to injury after brain death than other organs. In fact, approximately 80% of deceased organ donors are suitable kidney donors, 60% are suitable liver donors, and 20-30% are suitable lung donors. As a result, over 16,000 kidney and 6,000 liver transplants were performed in the US in 2012 compared to 1,700 lung transplants. The number of lung transplants performed annually has grown modestly in recent years, but this growth has been superseded by a greater magnitude of growth in the number of patients listed for transplantation. Thus, the severity of the lung organ shortage has persisted despite increases in the number of transplants performed. Unfortunately, this disparity between donor organ shortage and need results in deaths on the waiting list.
The lung allocation scoring (LAS) system was implemented in 2005 to reduce mortality on the waiting list and maximize the transplant benefit. However, mortality on the waiting list remains considerable. In fact, the death rate among patients waiting for a lung transplant has increased in the past 2 to 3 years to 15 deaths per 100 waitlist-years. While it is difficult to compare mortality on the waiting list under the LAS system to the era before the LAS when allocation was based solely on waiting time, many believe that the recent increase in waitlist mortality reflects a change in clinical practice where sicker and older patients with more advanced lung disease are being listed for transplantation. It is also likely that the old practice of listing patients early in anticipation of a long waiting time diluted waitlist mortality under the old allocation system. Nevertheless, it is clear that some patients listed for transplantation will die before having a transplant as a result of the donor organ shortage despite the current allocation system.
Over the years, transplant programs have adapted their practices to meet the challenges of lung transplantation and provide their patients the best clinical care. To address the donor organ shortage and the ever-present risk of death on the waiting list, most programs have liberalized their criteria of an acceptable donor organ, and the use of so-called “extended-criteria or marginal donors” has proliferated over the years. In fact, many lungs that are currently accepted for transplantation would have been declined 20 years ago, and the use of extended-criteria donors has allowed the increase in the number of transplants performed. Importantly, outcomes after transplantation have also improved, and outcomes of recipients of extended-criteria donors have been similar to recipients of ideal donors.
In general, a donor smoking history less than 20 pack-years, the equivalent of one pack of cigarettes daily for 20 years, is considered acceptable whereas a smoking history greater than 20 pack-years is thought to confer added risks. Although smoking is the leading cause of emphysema and lung cancer, the reality is that most smokers do not develop lung disease. This suggests that lungs from a donor who smoked may be perfectly suitable for transplantation. Investigators at Temple University recently published a study of the UNOS database comparing the outcomes of patients transplanted with lungs from donors who smoked more than 20 pack-years to those transplanted with lungs from donors who never smoked or smoked less than 20 pack-years. There was no difference in survival, peak lung function, or the development of chronic rejection after transplantation between the two groups. Importantly, there was also no difference in the number of deaths due to cancer between the two groups. A limitation of this study, due to the constraints of the UNOS database, is that donors who never smoked and those who smoked less than 20 pack-years are combined together while donors who smoked more than 20 pack-years are not further categorized according to the number of pack-years. So, it is difficult to determine if there is a number of pack-years that confers an unacceptable risk. Nonetheless, the findings suggest that the use of lungs from donors who smoked more than 20 pack-years is acceptable.
The donor organ shortage remains a leading challenge in lung transplantation and the main obstacle to transplantation for patients with advanced lung disease. Expanding the donor pool by increasing organ donation awareness and the use of extended-criteria donors have alleviated some of the critical donor organ shortage, but the need remains far greater than the supply. Ultimately, risks and benefits have to be considered, but transplantation carries inherent risks that cannot be over-emphasized.