Mobilized Peripheral Blood Transplants May Overtake ABMT Within Two Years

Within the next 2 years, peripheral blood will replace bone marrowas the medium for autologous transplants, predicted Malcolm A.S.Moore, DPhil, at a press briefing co-sponsored by the Cancer ResearchInstitute and Immunex Corporation.

Although numerous issues remain to be resolved for allogeneictransplants, principally graft-vs-host disease (GVHD), he believesthat within the next decade, the technology for mobilizing peripheralblood will be sufficiently advanced to render both autologousand allogeneic bone marrow transplants obsolete.

Once refined, the peripheral blood procedure will be considerablysimpler than bone marrow transplant because it can be done repeatedly,without general anesthesia, and because a considerably smallersample can be expanded for multiple transfusions, said Dr. Moore,Head of the Laboratory of Developmental Hematopoiesis, MemorialSloan-Kettering Cancer Center.

The key, he said, is to stimulate stem cells to appear in theperipheral blood using colony-stimulating factor treatment. Dr.Moore, who discovered granulocyte colony-stimulating factor (G-CSF),cited three such factors currently available: G-CSF, granulocyte-macrophageCSF(GM-CSF), and stem-cell factor.

None of these, however, accelerate regeneration of platelets.A newly discovered growth factor, thrombopoietin, does seem todo so, and more effectively than the interleukins that have thusfar been tried, he said.

Dr. Moore is convinced that many growth factors are needed toproduce the desired effect. He is working with various combinations--whathe terms a "cocktail"--to direct development of specificcell populations and to expand them, ex vivo, for reinfusion betweenchemotherapy cycles.

In a randomized trial involving patients with metastatic breastcancer at Memorial Sloan-Kettering, the post-treatment periodof hematopoietic recovery was shortened to 10 to 12 days usingmobilized peripheral blood (compared to 15 to 20 days with bonemarrow transplant). He cautions that the timing of treatment cyclesand infusion of "boosted" blood is crucial, and thatthese aspects of treatment still must be fine-tuned.

Umbilical Cord Blood

An even more abundant source of stem cells than peripheral bloodis umbilical cord blood. "It is an intrinsically rich sourceof stem cells so, unlike peripheral blood, patients do not needto be treated with growth factors," Dr. Moore said. Withumbilical cord blood, there is reduced risk of GVHD, and becausethe cells are younger, they have greater potential for division,he added.

Cord blood withdrawn and frozen can be used at a future time toprovide needed cells for either autologous or allogeneic transplant.The New York Blood Center has been awarded an NIH grant to investigatethis application, and has already done 20 allogeneic transplantsusing cord blood, he said.