Selecting Initial Treatment
Generally speaking, if the estimated 1-year TRM for SCT is less than 20%, transplantation should be considered optimum therapy. This situation usually exists in young patients who have closely matched related donors. If the TRM is between 20% and 40%, IFN-α may be the best treatment choice, reserving SCT for those who do not respond to 12 months of IFN-α therapy. If the estimated TRM exceeds 40%, transplant should be delayed until signs of disease acceleration occur.
CML in Blast Crisis
The prognosis for patients with CML in blast crisis remains dismal. Virtually all chemotherapy agents used for treating AML have been tried in patients with disease in myeloid blast crisis. Objective response rates following high-dose cytosine arabinoside or other anti-AML regimens are 20%–40%, with a median survival of 4–6 months. A recent study of 162 CML patients in non-lymphoid blast crisis found a 22% objective response rate and a median overall survival of 22 weeks. In this study, there was a slight benefit from decitabine (an experimental agent) versus other intensive chemotherapy agents, suggesting a role for decitabine in future trials. Some centres will consider SCT if blast crisis patients return to a second chronic phase following treatment with chemotherapy.
Patients with lymphoid blast crisis CML respond to treatment better than those with other forms of disease. When treated with regimens used for ALL, the complete remission rate is about 60%. Approximately 50% of patients have a cytogenetic response, with a remission duration of 9–12 months. The combination of vincristine and prednisone, as well as vincristine, doxorubicin and dexamethasone have been used to treat patients with disease in lymphoid blast crisis (Derderian 1993). Patients who enter a second chronic phase can be considered candidates for SCT.