PERIPHERAL-BLOOD STEM-CELL TRANSPLANTATIONS - PAST, PRESENT AND FUTURE

Since the first successful attempt in 1985, peripheral blood stem cell transplants are increasingly performed worldwide and should now be co nsidered as an essential therapeutic weapon against onco-hematological diseases. Their development has benefited greatly from a rapid concom itant advance of experimental knowledge regarding the nature of hemato poietic progenitor cells. For this reason and also for technical ones, until now these transplants generally have been autotransplants. Alth ough one of the main reasons to use blood rather than bone marrow-deri ved stem cells was that they might carry less risk of relapse than aut ologous bone marrow cells, the lack of clinical randomized trials and/ or the short follow-up make conclusions difficult so far in terms of d isease-free and overall survival. Probably the risk of relapse also de pends on the type of disease, on prior chemotherapies, on the type of peripheral stem cell mobilization regimen and on the number of blood-d erived cells transplanted. Nevertheless, there are several major clini cal indications for autologous blood stem cell transplant: acute non-l ymphoblastic leukemias (ANLL), low-grade non-Hodgkin's lymphomas, mult iple myeloma, some solid tumors, and even chronic myeloid leukemia. No w well-demonstrated advantages add a socioeconomic interest to this te chnique. The speed of post-transplant hematopoietic recovery induces a briefer hospitalization and a lower cost of the procedure, which repr esents '' per se'' important progress. Furthermore, the increasing use of hematopoietic growth factor(s) at time of blood-derived cell mobil ization should increase the safety of the procedure. Also new trends a re currently being developed: autotransplants with purified peripheral CD34+ cells; addition of adjuvant immunotherapy to induce graft-versu s-tumor effect, which is lacking in autotransplant; and transplants us ing allogenic umbilical cord blood progenitors. Allogenic blood cell t ransplants might also be developed, provided that blood cells would be less likely to cause graft-versus-host disease (GVHD) than bone marro w, which is still not verified. Finally, the use of blood-derived cell s as a vehicle for gene therapy should develop greatly in the near fut ure.