Cord Blood Transplants: A Treatment Option for Adults?
Three new studies - two recently published in the New England
Journal of Medicine and a third in the journal Blood - provide evidence
that adults with leukemia who cannot find a bone marrow donor may be helped by
a cord blood transplant.
Like bone marrow, umbilical cord blood contains stem cells that
can produce healthy blood cells. When a patient with a blood disorder undergoes
high-dose chemotherapy or radiation, both the diseased cells and the patient's
own stem cells are destroyed. Like a bone marrow transplant, a cord blood
transplant enables the patient's body to begin producing healthy new blood
cells again.
However, the number of stem cells in a unit of umbilical cord
blood is small. Thus, a cord blood transplant has generally been considered a
treatment option only for children and small adults. These new studies
challenge that assumption.
The first study, conducted by researchers affiliated with the
International Bone Marrow Transplant Registry and the New York Blood Center,
looked at 150 adults who were transplanted with cord blood stem cells and 450
adults who were transplanted with bone marrow. All of the donors were unrelated
to the patient.
Patients who had a matched adult donor fared best. A matched donor
is one who has the same set of markers on his cells (called human leukocyte
antigens or HLA) as those on the patient's cells. Patients who received a
mismatched transplant, whether it was cord blood or a bone marrow transplant,
experienced more complications and a somewhat higher mortality rate. However,
the authors concluded that both should be considered acceptable treatment
options if the patient does not have a matched donor.
A second study conducted by the European Blood & Marrow
Transplant Group reached a similar conclusion. The group compared 98 adults who
were transplanted with cord blood to 584 adults who received bone marrow from a
matched unrelated donor. Ninety-four percent of the cord blood transplants were
mismatched. Although the cord blood transplant patients took longer to begin
producing healthy blood cells after transplant, the incidences of
complications, transplant-related mortality, relapse and leukemia-free survival
were not significantly different from the incidences in patients who received
bone marrow.
The third study, reported by researchers at the University of
Minnesota, explored whether transplanting patients with two different units of
cord blood at the same time is safe. Combining two units of cord blood
increases the number of stem cells transplanted into a patient, and could
potentially shorten the time it takes for the stem cells to begin producing
healthy new blood cells. Although the number of patients included in the study
was small (23), the researchers concluded that this approach is safe, and may
allow many more patients access to transplant. A larger study is needed to
confirm these encouraging results.
These studies thrill 57-year-old Stephen Sprague, whose life was
saved by a cord blood transplant in 1997. "More than seven years ago, a
pioneering clinical trial using cord blood was able to cure me of my leukemia
after I had run out of options," Sprague recalls. "It's encouraging to finally
see what was once an experimental high-risk treatment has now become a viable
option for other adult patients."
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