Myeloablative Allogeneic Transplantation In

Texts and review articles commonly provide a wide range of survival and mortality rates in patients with CML who undergo allogeneic transplantation. 1-5 The lower range of survival and higher range of mortality rates generally quoted are derived from studies of patients who underwent transplantation 20 or more years ago.6-11 Results have improved with time.6-12

Allogeneic transplantation using myeloablative regimens works through two different mechanisms. The myeloablative regimen eradicates nearly all malignant cells in most patients. A retrospective analysis of iden tical twins with CML demonstrated a 3-year probability of leukemia-free survival of 59%, compared to 61% for HLA-identical sibling transplants.14 Although the 3-year probability of treatment-related mortality was only 3% for the twins, their risk of relapse was 40% at three years, compared to 7% for a cohort of HLA-iden-tical sibling transplants. The fact that some patients with CML are cured by syngeneic transplants demonstrates that myeloablative therapy alone can eradicate all malignant cells in some patients. The higher relapse rate indicates a role for allogeneic cells in complete eradication of disease. Lower relapse rates in patients who undergo unrelated transplants and in those who develop graft-versus-host disease15-17 further support the importance of the allogeneic effect. The sustained elimination of Ph+ cells following infusion of donor lymphocytes, in patients who relapse following transplantation, is clear demonstration of the potency of the allogeneic affect.18-20

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