History

CML has traditionally been the most common indication for allogeneic transplantation and the curative potential of allo-BMT in this disease is well established. The majority of preparative regimens used for leukemia were developed to treat this disease. It was also the model for adoptive immunotherapy in the form of graft-versus-tumor that established the practice of donor lymphocyte infusion. The development of ima-tinib has substantially decreased the number of patients who are treated with stem cell transplants, but it remains the standard bearer for patients treated with curative intent.

Autologous transplant plays a less established role in CML management than allogeneic BMT. However, given the lack of potential histocompatible donors for many patients, as well as the tendency for the disease to present after the age of 50 years, autologous transplant has enjoyed a fair amount of interest in terms of offering the potential benefits of myeloablative therapy to more patients with CML. This is particularly true for advanced phase disease, for which there are no effective therapies outside of transplant. The initial reports of autologous transplant in CML used stem cells frozen from chronic phase to rescue patients treated with myeloablaative chemotherapy at a time of blast crisis. A second chronic phase ensued in many patients, but relapses typically occurred in less than 1 year.50 Due to persistence of leukemia following autologous transplantation, attempts using a number of in vitro purging agents ensued, none of which consistently provided protection against relapse. Ultimately the development of imatinib may have rekindled interest in harvesting of PCR negative stem cells for use in future because of imatinib failure. Given the low toxicity of the drug, however, there is little interest in autologous transplant as initial therapy.

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