Successful treatment with imatinib mesylate of a CML patient in megakaryoblastic crisis with severe fibrosis.

The prognosis of patients with chronic myeloid leukemia in blastic crisis (CML-BC) remains extremely poor, and multiagent chemotherapy regimens commonly used to treat acute leukemia offer only short-term benefits. Therefore, the advent of the novel molecularly targeted anticancer agent imatinib mesylate is a breakthrough in CML therapy. We present a CML patient in megakaryoblastic crisis with severe myelofibrosis, who was treated with imatinib at a dosage of 400 mg/day and achieved complete remission together with a marked regression of myelofibrosis after 1 month. The effect of imatinib on the long-term prognosis remains unclear, although the agent is clearly a promising drug for treating CML-BC even in cases of myelofibrosis.