A study led by researchers at Baylor College of Medicine has revealed that since the implementation in 2005 of a medical need-based allocation system for donor lungs, double-lung transplantation has been associated with better graft survival than single-lung transplantation in patients with idiopathic pulmonary fibrosis (IPF). However, there has been no survival difference between double- and single-lung transplant recipients in patients with chronic obstructive pulmonary disease, or COPD.
The research, led by Dr. Hari R. Mallidi, associate professor of surgery at Baylor College of Medicine and chief of the division of transplant and assist devices, appears in the latest issue of the Journal of the American Medical Association.
“Despite the introduction of need-based organ allocation for lung transplantation in 2005, patients continue to die while waiting for an organ to become available. Our study used the latest techniques of outcomes analysis to determine risk factors for survival following lung transplant,” Mallidi said. “When these factors are taken into consideration, they may allow for a more rational use of the available donor organs such that the benefit of lung transplantation can be extended to the largest group of patients possible.”
Before 2005, lung transplant allocation in the United States was based on accumulated time on the lung transplant waiting list after matching for ABO blood type. In response to increasing wait times, the U.S. Department of Health and Human Services mandated the development of an allocation system based on medical need instead of waiting time. The resulting system—the Lung Allocation Score (LAS) organ allocation algorithm—was implemented in May 2005. It takes into account various measures of a patient’s health to determine patient priority on the waiting list.
Mallidi and his research colleagues reviewed data from the United Network for Organ Sharing thoracic registry to summarize the demographics and outcomes in adults with IPF or COPD who underwent single- or double lung transplantation in the United States between May 2005 and December 2012.
The researchers identified 4,134 patients with IPF (of whom 2,010 underwent single-lung and 2,124 underwent double-lung transplantation) and 3,174 patients with COPD (of whom 1,299 underwent single-lung and 1,875 underwent double-lung transplantation).
Of the patients with IPF, 33.4 percent died and 2.8 percent underwent retransplantation; of the patients with COPD, 34.0 percent died and 1.9 percent underwent retransplantation. Further analysis indicated that double-lung transplants were associated with better graft survival in patients with IPF (adjusted median survival, 65.2 months vs. 50.4 months) but not in patients with COPD (adjusted median survival, 67.7 months vs. 64.0 months).
The researchers said the findings show the interaction between diagnosis (COPD or IPF) and treatment type (single- and double-lung transplantation) was significant, supporting the finding that the benefit of double-lung transplantation may differ by diagnosis.
Other factors affected graft failure such as age of the recipient and donor, excessively high or low body mass index, poor 6-minute walk test performance and pulmonary hypertension (in patients with COPD). There were also factors that helped survival rates such as undergoing transplantation at a high-performing and high volume transplant center and receiving a locally allocated organ, and donor-recipient race match (in patients with IPF).
IPF is a disease in which the deep tissue of the lungs becomes scarred over time. It can get progressively worse, and there is no cure. COPD also is a progressive disease that causes difficulty breathing.
This research was conducted as a collaboration between lung transplant surgeons and physicians at Baylor College of Medicine and Stanford University. Others involved in the research included Drs. Justin M. Schaffer, Bruce A. Reitz and Roham T. Zamanian of Stanford and Dr. Steve K. Singh of Baylor.