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.