Autologous bone marrow transplantation in acute leukemia

Autologous bone marrow transplantation (ABMT), which was developed in the past decade, is currently under investigation for the treatment of leukemias, lymphomas, and a few solid tumors. It consists of engrafting a patient, after ablative chemotherapy and/or total-body irradiation (TBI), with marrow taken from the patient at a propitious time in the history of the disease and usually cryopreserved. This technique has two major consequences: ABMT by reducing the length and variability of posttreatment aplasia can be considered a super hematologic support. It allows the use of chemotherapeutic agents and/or TBI at doses that surpass the dose for effecting the threshold of myelotoxicity. Therefore, a greater tumor cell kill can be expected at a reasonably low cost in terms of toxicity. In patients with acute leukemia (AL), however, the contribution of ABMT may go far beyond. In the initial trials (1974-79), the marrow of patients with AL was collected during complete remission and cryopreserved, with the idea of preserving "the remission status." At relapse this marrow was re-infused after high-dose chemotherapy and/or TBI, for achieving another complete remission. The result could be considered a chronologic chimera; the autograft, which had stem cells younger than those of the organism, reproduced, over the course of a few months or years, the evolution of the remission during which it was collected. As predicted, however, all patients who received this treatment eventually relapsed. For a more aggressive technique, some teams gave autografts to patients earlier, during remission, to allow ablative therapy in the consolidation mode; the whole procedure, including the pretransplant cytoreductive regimen, was modeled on that of allografting. Because allogeneic bone marrow transplantation currently offers the best chance of long-term survival but remains severely restricted, by age and availability of an HLA-identical donor, to less than 10% of the patients, ABMT may be considered an alternative source of stem cells to the other patients. In addition, ABMT avoids the risks of graft-versus-host disease with its associated immunosuppression. However, one major impediment to effective ABMT may be the persistence of leukemia cells in the marrow autograft, although the marrow was collected during earlier remission. The recent development of numerous techniques to cleanse the marrow prior to ABMT has considerably increased the possibility of ABMT becoming a major tool in the cure of leukemia. This report reviews the early data and essentially focuses on recent results of ABMT effected in or done in remission with use of cleansed and uncleansed marrow.