Having both lungs replaced instead of just one is the
single most important feature determining
who lives longest after having a lung transplant, more than
doubling an organ recipient's chances of
extending his or her life by over a decade, a study by a
team of transplant surgeons at Johns Hopkins
shows.
The finding is potentially controversial, researchers
say, because there is already a shortage of
organ donors, and more widespread use of bilateral lung
transplants could nearly halve the potential
number of beneficiaries. Though more than 1,400 lung
transplants occurred in the United States in
2008, another 2,000 Americans remain on lung waiting lists,
while 80 more are waiting for both a
heart and lung.
"Our results suggest that double-lung transplants have
a long-term advantage, and surgeons
should consider bilateral lung transplants whenever
possible," said study senior investigator and
transplant surgeon Ashish Shah. But, Shah noted, not
all lung recipients necessarily need a bilateral
transplant. "Many people with chronic obstructive pulmonary
disease, including emphysema and
different kinds of pulmonary fibrosis, can survive with
just one lung being replaced, while other lung
diseases, such as cystic fibrosis, usually require
transplantation of both lungs. But double-lung
transplants clearly perform better over time," he said.
"What we're really after here is to find as many
factors as possible that support long-term
survival, so that we maximize the gains in average lifespan
for all our patients," Shah said.
Among the team's other key findings, presented April
22 in Paris at the annual meeting of the
International Society for Heart & Lung Transplantation, are
that a perfect or near-perfect match
between the donor's and recipient's immune-activating
protein antigens and having a college education
increase chances for long-term survival by 38 percent and
40 percent, respectively.
The study, believed to be the most widespread search
ever conducted for factors that may
extend the life of lung transplant recipients, is among the
first to emerge from an analysis of 836 so-called long-term
survivors, men and women who have lived at least a decade
after lung transplant surgery between 1987 and 1997, an
extended period for which detailed medical histories are
now available.
Seventeen percent of all recipients survive this long
or longer with their new lungs, a figure
that Shah, an associate professor at the Johns Hopkins
University School of Medicine and its
Heart and Vascular Institute, said is "pretty good, but
not good enough" and is the result of advances made
in the last two decades with immune-suppressing drugs that
prevent the recipient's body from
rejecting the transplant.
"Until now, we knew how best to ensure that transplant
recipients survive for the first few
months after surgery, avoiding infection of the
transplanted lung and then staying healthy for the
next two years to five years. But we never really knew what
factors distinguished the long-term
survivors from those who succumbed earlier, to either organ
rejection or death," said Shah, who has
performed more than 100 lung transplants in the past
decade.
Lead study investigator Eric Weiss says that a
patient's education, though key, more likely
masks some other factor or combination of factors that
accounts for the increased longevity. Possible
explanations, he says, are that better-educated people may
have better health insurance and access
to care than those with less formal schooling, or that
people with degrees are better at keeping their
physician appointments on schedule, taking their
medications as prescribed and sooner alerting their
physicians to problems.
"Our results are a reminder to both patients and
physicians that we still have a lot to learn
about how best to prolong lung transplant survival, and
that we need to be constantly evaluating our
procedures to determine what is in the patient's best,
long-term interests," said Weiss, a postdoctoral
research fellow in
Cardiac Surgery at Johns Hopkins.
Indeed, Weiss points out that a key advantage in
double- over single-lung transplants is that
residual disease is not left behind in the spared lung.
Moreover, when both lungs are replaced, the new
lungs, which must breathe as a pair, are already adapted to
each other.
The vast majority of the lung transplants performed by
Shah's team at The Johns Hopkins
Hospital involve the fully paired organs, including 15 of
17 in 2008, 20 of 22 in 2007 and 20 of 23 in
2006.
In the latest study, long-term survival for lung
recipients was also upped when their immune
systems were "highly compatible" with those of their
donors, with at least five of six so-called human
leukocyte antigens the same. HLAs are proteins that sit on
the cell surface and act like a secret pass
code among the body's cells, triggering the body's immune
system to reject anything that's not
recognizable as its own. The better the match, Weiss says,
the better are chances for
immunosuppressive drugs to work over the long term at
preventing organ rejection.
The study analysis involved a detailed review of the
patient records for all single- and double-
lung transplants performed in the United States and Canada
from 1987 to 1997. The data came from
the United Network for Organ Sharing, which allocates
donated organs across the country.
Weiss says the team next plans to evaluate what
aspects of education make the difference in
long-term survival, with the goal of identifying
independent factors that can influence better
adherence to drug treatment plans or that could potentially
be altered in people to extend the amount
of time they can potentially live with their new organ.
Funding for the study was supplied in part by the
Health Resources and Services
Administration, National Institutes of Health and Joyce
Koons Family Fund for Cardiac Surgery
Research.
In addition to Shah and Weiss, Johns Hopkins
researchers involved in this study were Jeremiah
G. Allen, Christian Merlo and John Conte.