Pocket Drug Guide

Stem-cell transplantation includes both bone marrow transplantation and peripheral blood cell transplantation. Stem-cell transplantation initially involves the collection of precursor hematopoietic cells (stem cells) from either the bone marrow (resulting in a bone marrow transplant) or the peripheral blood (resulting in a peripheral blood cell transplantation). The stem cells can be harvested either from a healthy HLA-matched donor (allogeneric stem-cell transplantation [allo-Stem-cell transplantation]) or from the patient (auto-Stem-cell transplantation). The stem cells are preserved while high-dose myeloablative chemo- and radiotherapy is administered. The cells are then reinfused into the patient, whereupon they migrate to the bone marrow to aid hematopoietic recovery and “rescue” the patient from lethal myelotoxicity.

In the treatment of leukemia, the aim of high-dose therapy and transplantation is to destroy the defective blood progenitor stem cells and replace them with healthy, nonleukemic cells. In autologous peripheral stem-cell transplantation (APSCT), the destruction of the patient’s bone marrow cells also destroys the patient’s own T cells, preventing the patient from rejecting the donor progenitor stem cells.

In the context of this report, we consider PSCT to include both the myeloablative treatment and the reinfusion of progenitor stem cells.

Myeloablative Regimens

Two common myeloablative regimens are used in the treatment of chronic myelogenous leukemia to destroy patients’ bone marrow prior to PSCT: total body irradiation and cyclophosphamide (TBI-CY) or busulfan and cyclophosphamide (BU-CY).

In patients who undergo transplantation in the chronic phase of chronic myelogenous leukemia, the two regimens have comparable transplant-related mortality and efficacy rates, but the BU-CY regimen is reportedly better tolerated. Patients with more advanced disease who are treated with BU-CY have worse transplant-related mortality and survival rates than those treated with TBI-CY.

Autologous Progenitor Stem-Cell Transplantation

Unlike allo-Stem-cell transplantation, au-to-Stem-cell transplantation is not curative. However, auto-Stem-cell transplantation can effectively induce short second chronic phases in patients with accelerated- or blastic-phase disease. The use of auto-Stem-cell transplantation in chronic-phase patients is considered experimental.

A study analyzed the outcome of 581 patients receiving auto-Stem-cell transplantation for chronic myelogenous leukemia in the first chronic phase reported to the EBMT between 1983 and 1998. Of 207 patients evaluable for cytogenetic analysis within six months of Stem-cell transplantation, 17% achieved a cytogenetic response, 16% achieved a major response, 36% achieved a minor response, and 31% displayed no cytogenetic response. Results of the cytogenetic analysis within one to two years of Stem-cell transplantation were available for 117 patients, the majority of whom received interferon-a post Stem-cell transplantation. Of these patients, 15% achieved a cytogenetic response, 15% achieved a major response, 20% achieved a minor response, and 50% displayed no cytogenetic response. Patients in cytogenetic response or major remission at one to two years post Stem-cell transplantation had a ten-year survival of 66% compared with 36% for patients in minor remission or those who displayed no response. The five-year survival for patients receiving interferon-a post Stem-cell transplantation was 72% compared

with 61% for patients not treated with interferon-a. Out of 155 patients refractory to interferon-a pre Stem-cell transplantation, 70% achieved a cytogenetic response post Stem-cell transplantation; this response was complete or major in 31%.

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