Implications of imatinib mesylate for hematopoietic stem cell transplantation

The ability of allogeneic bone marrow or blood stem cell transplantation (SCT) to induce long-term remission or cure of chronic myeloid leukemia (CML) is well established. However, the use of this treatment is limited by the availability of suitable human leukocyte antigen (HLA) identical siblings or matched unrelated donors (MUD). As a consequence only a relatively small proportion of CML patients are eligible for a transplant, and of these not all are cured. The preliminary results of trials using the new Bcr-Abl kinase inhibitor imatinib mesylate (formerly CGP57-148B, STI571, Gleevec) to treat CML are very encouraging. However, a number of important questions cannot yet be answered: Can imatinib mesylate induce durable molecular remissions? Can the drug prolong survival in comparison with other nontransplant treatments? and, can it actually cure CML patients? Until answers to these questions are available, SCT and use of interferon-alfa (IFN-alpha) alone or in combination (perhaps with imatinib mesylate) must remain major therapeutic options. I summarize here the advantages and disadvantages associated with currently available therapy. I review three different approaches to initial treatment of the CML patient diagnosed in chronic phase, and make a tentative recommendation for one of these options. It is likely that the situation will alter considerably in the foreseeable future.