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Stem Cells Allow Autotransplants in CML

Stem Cells Allow Autotransplants in CML

SAN DIEGO, Calif--Researchers have demonstrated that in at least
some patients with chronic myelogenous leukemia (CML), benign
hematopoietic stem cell progenitors coexist in the marrow with
malignant cells, creating the possibility that autologous bone
marrow transplantation can be used to treat the disease, Phillip
McGlave, MD, said at a conference sponsored by the University
of California, San Diego Cancer Center and UCSD School of Medicine.

Bone marrow transplant provides the only curative therapeutic
approach for CML. However, finding a matched donor is often difficult,
and patients must be physically able to withstand the complications
associated with donor transplants, including graft-versus-host
disease, said Dr. McGlave, director, Adult Marrow Transplant Program,
University of Minnesota Health System.

To eliminate some of the problems of allogeneic transplants, investigators
have attempted to isolate the patient's own benign hematopoietic
stem cells for autologous transplantation. If a sufficient number
of these cells can be obtained from the patient's peripheral blood
or marrow, they can be used to "rescue" the patient
following the intensive chemoradiotherapy that kills their malignant
counterparts in the body.

To date, 200 "first generation" autologous transplants
for the treatment of CML have been performed at eight centers
in Europe and North America. In this group of patients, the survival
rate (at a median of 4 years post-transplant) for those with chronic
phase CML was 59%, Dr. McGlave reported.

Improved survival was seen in those patients transplanted within
12 months of diagnosis and in those less than 40 years of age.
No survival advantage could be attributed to any specific method
of pretransplant marrow preparation or to the use of peripheral
blood rather than bone marrow as a source of stem cells.

Dr. McGlave stressed that the patients with successful engraftment
were not disease-free; in fact, "virtually all had some evidence
of CML when they were assessed--either the Philadelphia chromosome
(Ph positive metaphases) or, in some cases, clinical evidence
of CML," he noted.

Dr. McGlave added that in some patients, the response to treatment
was not complete, resulting in early relapse. He cited malignant-cell
contamination of the transplanted bone marrow and the possible
absence of a graft-versus-leukemia effect as possible causes of
relapse.

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