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Bone marrow or hematopoietic cell transplantation (BMT or HCT) is a potentially curative therapy for a wide variety of life-threatening congenital and acquired hematopoietic stem cell disorders and neoplastic diseases. With the development of human leukocyte antigen (HLA) typing to identify suitably matched donors, advances in tolerability and efficacy of conditioning regimens, improvements in supportive care, and advances in the prophylaxis and treatment of graft-versus-host disease (GVHD), clinical HCT became a reality. Many of the initial clinical HCT efforts were directed toward severe aplastic anemia and acute leukemia (which remains the paradigm for allogeneic HCT in adults). However, the demonstration of lasting donor lymphohematopoietic reconstitution, the powerful cytoreductive effect of intensive pretransplantation conditioning therapy, and the exploitation of a potent immunologically-mediated graft-versus-tumor (GVT) effect led to the successful application of HCT as up-front and salvage therapy for the many hematologic malignancies and other disorders shown in Table 38-1. Some applications of HCT are potentially curative, e.g., allogeneic transplantation for acute myeloid leukemia (AML). In other settings, HCT is primarily utilized to lengthen disease-free intervals without expectation of cure, e.g., autologous transplantation for multiple myeloma. In parallel with the above advances, the use of hematopoietic cell transplantation has expanded yearly. In 2009, more than 26,000 transplants were performed worldwide, over 15,000 of these being allogeneic HCTs (1).
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The principal functions of HCT are to provide:
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Rescue (i.e., by the infusion of pluripotent hematopoietic progenitor cells in the setting of cytoreductive chemotherapy that eradicates malignant cells but also ablates stem cells and other hematopoietic bone marrow elements)
Replacement (i.e., of a diseased hematopoietic stem cell population by healthy stem cells capable of regeneration of multiple hematopoietic lineages)
An immunologic platform (As mixed lymphohematopoietic chimerism often occurs after less intensive conditioning, HCT may be envisioned as creating an immunologic platform for adoptive cellular therapy. Subsequent manipulation may occur through donor lymphocyte infusions (DLI), expansion, or depletion of T-cell subsets (e.g., regulatory T cells), or selection of NK and dendritic cell subsets in order to augment GVT effects while minimizing GVHD) (...