ABSTRACT
I) GENERAL PRINCIPLES Over the past 25 years, a large number of intensive conditioning regimens re
quiring hematopoietic stem cell transplantation (HSCT) have been developed. The earliest regimens were developed for the allogeneic transplantation of acute leu kemia, and primarily employed total body irradiation (TBI)/chemotherapy combi nations. However, over the past decade, a proliferation of mosdy chemotherapybased regimens has occurred for use with autologous HSCT of solid tumors, lymphomas and AML. The design of conditioning regimens has generally been empirical and few randomized trials have established the superiority of one regi men over another. Thus, when choosing a conditioning regimen, a physician should consider a number of factors: is the regimen effective in the disease; does the patient have prior treatment or preexistent organ damage which may be exacer bated by specific cytotoxic drugs/TBI; and/or is immunosuppression needed to facilitate engraftment. A) Allogeneic
HSCT conditioning regimens must provide effective tumoricidal activity and suppress host immunity to prevent rejection of the allograft. Following en graftment, an allogeneic graft-versus-leukemia (GVL) effect provides additional and important antitumor activity. Commonly used cytotoxic agents include TBI, cyclophosphamide (CY), busulfan (BU), cytarabine (ara-c) and etoposide (VP). Immunosuppressive agents include TBI, cyclophosphamide, anti-lym phocyte antibodies (anti-thymocyte globulin (ATG)), steroids, cyclosporine A (CsA) and methotrexate. An exception to the need for conditioning regimens is sibling matched BMT for severe combined immune deficiency (SCID), where no host immunity or tumor exists.
