A new study led by U researchers found that most cystic fibrosis patients did not live longer after receiving lung transplants.
The findings showed that only the sickest transplant patients, those with less than a 30 percent expected five year survival rate, benefitted from a lung transplant.
The good news, said principle investigator Dr. Theodore Liou, is that less than 2 percent of all cystic fibrosis (CF) patients fall into this category, making it more likely that supply may eventually meet demand.
Liou, an assistant professor at the School of Medicine, was taking a math class to help his research when he came up with the idea for this study. With a background in lung diseases, Liou decided to apply mathematical modeling to help predict which CF patient would benefit from a lung transplant.
“People didn’t know who would do better,” Liou said, “it was mostly anecdotal?[or] they had this feeling.”
Cystic fibrosis is a hereditary disease characterized by abnormal mucous build-up, resulting in impairment of the lungs, pancreas and intestine. The median survival age is 32. The disease is also more common among Caucasians.
A lot of money has been spent collecting data on CF, Liou said. A patient database includes more than 90 percent of all CF cases.
“There’s no database like this for emphysema,” Liou said.
The study compared the survival rate of 468 CF patients who received transplants to that of non transplant patients. Only the 95 patients with the lowest five-year survival rate had a higher five-year survival rate after the transplant, but they also had a slightly lower short term survival rate. Other categories had either equal or lower survival rates after transplant than non-transplant patients.
The current system allows many healthier patients to receive transplants first. Patients of other diseases, such as emphysema, are placed on the first-come-first served waiting list for lung transplants along with CF patients. To ensure that their CF patients would receive transplants in time, physicians sometimes do not adhere to the criterion that determines priority and put the patients on the list prematurely.
“If doctors wait until their patients are ready for a transplant, the waiting list is so long, the patient could die,” said Dr. Bruce Marshall, a lung specialist at the School of Medicine and one of the researchers in the study.
The most common criterion used to determine eligibility for the waiting list is a measurement called forced expiratory volume 1 (FEV 1), which is the volume of air the patient can blow out in one second after inhaling a full breath.
Liou said there are several factors a physician can look at, but FEV 1 is the only objective measurement.
The researchers proposed using eight additional criteria that would better indicate how sick a CF patient is. Using these criteria, which include sex, age, weight, pancreatic function, presence of infections and diabetes mellitus, may shorten the waiting list from the current 1,500 to 150.
The researchers also think the system should be priority based with the sickest at the front of the line.
“Just like in the emergency room,” Liou said, “the sickest and most urgent are treated first.”
But the researchers warn that adoption of the new criteria probably won’t happen soon, especially if other disease programs don’t adopt a similar system.
“It’s going to take a lot of people coming together,” Liou said.